Fix appveyor documentation

Fix python install, cat java error log for kokoro build

* Adopt php_metadata_namespace in php code generator

The php_metadata_namespace is corresponded to the relative directory of
the metadata file. e.g., previously, the metadata file of foo.proto was
GPBMetadata/Foo.php. If the php_metadata_namespace is "Metadata\\Bar",
the metadata file will be Metadata/Bar/Foo.php.

* Handle empty php_metadata_namespace

Include version information in Windows binaries #3380

Appveyor MinGW build

[Java] Remove unsafe no-copy String allocation since it's not useful in rece…

Add .proto files to extract_includes.bat

* Throw error if user want to access message properties

* Fix typo

* Avoid direct check of class name

So that subclasses are also ok

* Use type hint in function signature.

use brew instead of easy_install in OSX (easy_install keep failing for a month)

Fix error in Clang UndefinedBehaviorSanitizer

Pointer Arguments to memcpy can not be null in UndefinedBehaviorSanitizer.
In this case, both the memory and the size was zero. This change allows
protoc to run under UndefinedBehaviorSanitizer.

Add mention to the "Build" section of the ReadMe of the requirement of installing an optional component to VS2017.

Fix MinGW build

Fix CMake build on Cygwin.

Make RepeatedField#delete_if consistent with Array#delete_if.

The class name was linked to the next word in the sentence.
"User\UserRequestis not found in descriptor pool."

Add a third-party RPC implementation: raster

* 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.

Add third-party RPC implementation: raster - a network framework supports pbrpc by 'service' keyword.

fixed typo

CMake: Update CXX Standard management

With this fix, Unity using IL2CPP should work with one of two
approaches:

- Call `FileDescriptor.ForceReflectionInitialization<T>` for every
  enum present in generated code (including oneof case enums)
- Ensure that IL2CPP uses the same code for int and any int-based
  enums

The former approach is likely to be simpler, unless IL2CPP changes
its default behavior. We *could* potentially generate the code
automatically, but that makes me slightly uncomfortable in terms of
generating code that's only relevant in one specific scenario. It
would be reasonably easy to write a tool (separate from protoc) to
generate the code required for any specific set of assemblies, so
that Unity users can include it in their application. We can always
decide to change to generate it automatically later.

Set ext.no_native = true for non mac platform

From:
https://github.com/rake-compiler/rake-compiler/issues/146#issuecomment-368539245

- merge loop for .h and .proto includes
- fix shellcheck errors