Signed-off-by: Xiang Dai <764524258@qq.com>

The CocoaPod (and source) have always support tvOS, but adding the project
makes it easier to run the tests and debug if there ever were an issue.

(not adding a watchOS project at the moment because Apple doesn't provide
 XCTest, so all it could do is build the library. We still support that,
 just can't "test" it.)

Some protos have enum values of "FOO" and "Foo", which the ObjC generation
then makes into the same thing. Just skip generating the enum element for
the duplicate as it would be a compile error because of the name collision.

The descriptors are still generated to support reflection and TextFormat
more completely.

Don't look up the TextFormat for the value as aliases can trip that
up, instead check the TextFormat names directly and then fetch the
value.

By putting the NSAssert behind a DEBUG flag we aren't copying filepaths
into release builds.

Just like fields, some extension fieldnames can be named such that they appear
to have meaning to ARC. Add the annotation to the compiler will get things
correct.

Add a bunch of extensions to allow inspection on generation to ensure things
are correct.

This should help the Swift compiler if these apis are used because it
changes the codegen to not need copies/retains.

This should help the Swift compiler if these apis are used because it
changes the codegen to not need copies/retains.

For deprecated fields, identify the deprecated field and source file in the deprecation message. For deprecated files, identify the deprecated file in deprecation messages of generated interfaces. This additional context in deprecation messages will help provide developers with more context which could help them seek recommended alternatives to deprecated interfaces.

In some cases proto files that want/need to use the objc_class_prefix option have
types that already have the prefix on a subset of their names. In this case we don't
want to duplicate the prefix.

Added tests for this (and prefixes in general).

Instead of using DEPRECATED_ATTRIBUTE from AvailabilityMacros.h, we should introduce a Google-specific Objective-C protobuf deprecation annotation. This helps address IWYU issues with using DEPRECATED_ATTRIBUTE and also enables allows clients to redefine the macro to treat protobuf warnings differently than other types of warnings (e.g., treating protobuf deprecation warnings as errors or ignoring them).

For messages that have multiple extension ranges, this will improve things
by avoiding repeated work.  For messages with a single range, it should
be a wash.

- Sort the list of set extensions once during serialization and reuse the list.
- Break out of the serialization loop as soon as the loop has moved pasted at
  accepted range for field ids.

If a proto has multiple extension ranges back to back, don't double
print the first items as they also are the ending range of the
previous.

Using NSCoding with a Message that has extensions is risky because
when reloaded, there is no way to provide a registry through the
NSCoding plumbing, so output a warnings to atleast give developers
a hint about the potential issues.

The builds were failing under Xcode 10 because of the new build system.
Even when reverted to the old build system, the build was failing
on the analyzer and swift bridging header, so it seems the general
logic for searching for things was changed in a way the setting does
not always cover.

- Disable HeaderMaps.
- Set user header search paths instead of system search paths.
- Turn off always search user paths (now recommended).

Tested in Xcode 10.1 and 9.4.1; both are able to build/pass with this.

We have code for converting C/C++/Objc keywords that appear in protos
to convert them so that they can be compiled.
One of the things we need to be careful of is accidentally overriding methods
that Apple declares in NSObject. It turns out that we have run into issues
where we conflict with "hidden" methods in NSObject or methods added by
categories. method_dump.sh collects all of the methods we care about for
macOS and iOS and dumps them into objectivec_nsobject_methods.h which
is then included in objectivec_helpers.cc as part of the build.

Added a pile of tests to verify that conversions are happening as expected.

No changes were needed, but since the Xcode projects pick up the updated
setting, the tests require a newer Xcode that supports Swift 4.

This is being done because Xcode 10 starting warning about Swift 3 support
going away in the future, so we might as well do the updates since most
folks shouldn't be on those really old Xcode versions any more.

Follow ObjC conventions and how the generated header labels things by
copying NSStrings/NSData fields when setting them.

Causes a warning in newer Xcodes.

If you make up a module map for Objective C protocol buffers, the compiler will complain about missing a declaration for GPBUnknownFieldSet which is used in this file.

* Remove/replace travis references.

* objectivec: Quash -Wself-assign

* objectivec: Set -Wno-vla when building

Objective-C protobuf uses VLAs for performance reasons. Ensure Clang
doesn’t complain about them.

* Update code to work for Xcode 10b

* Update README and test scripts to mention that Xcode 7 is no longer supported

* Update code to work for Xcode 10b

* Update README and test scripts to mention that Xcode 7 is no longer supported

Added new API to GPBEnumDescriptor to enable introspection of enum values.

Refactored implementation so that this contains a minimum of added code.

Clarified comments regarding behavior in the presence of the alias_allowed option.

Added unit tests for new functionality and for the alias case.

* Fix memory leak of exceptions raised by RaiseException()

Currently exceptions raised by RaiseException() is never deallocated because:

* ARC is disabled for this library: https://github.com/google/protobuf/blob/master/BUILD#L913
* It is constructed with `+alloc` but is never `-release`d.

This change fixes the issue by using `-[NSException exceptionWithName:...]` instead, which returns an autoreleased instance, so it is deallocated properly.

* Fix format.