About 1.5% of all IEEE754 single-precision numbers require nine
decimal digits to represent accurately.

Building the protobuf compiler with Bazel fails to resolve the unqualifed "string"s in java_options.h:

```
ERROR: .../external/com_google_protobuf/BUILD:248:1: C++ compilation of rule '@com_google_protobuf//:protoc_lib' failed: Process exited with status 1 [sandboxed].
In file included from external/com_google_protobuf/src/google/protobuf/compiler/java/java_context.h:41:0,
                 from external/com_google_protobuf/src/google/protobuf/compiler/java/java_enum_field_lite.cc:38:
external/com_google_protobuf/src/google/protobuf/compiler/java/java_options.h:59:3: error: 'string' does not name a type
   string annotation_list_file;
   ^
external/com_google_protobuf/src/google/protobuf/compiler/java/java_options.h:62:3: error: 'string' does not name a type
   string output_list_file;
   ^
Use --strategy=CppCompile=standalone to disable sandboxing for the failing actions.
INFO: Elapsed time: 41.487s, Critical Path: 6.20s
//interpreter:eval_test                                               NO STATUS

Executed 0 out of 1 test: 1 was skipped.
```

fixed_address_empty_string symbol is used in an inline function.
We have to export it to avoid undefined reference link errors.

* Add new file option php_namespace.

Use this option to change the namespace of php generated classes.
Default is empty. When this option is empty, the package name will be
used for determining the namespace.

* Uncomment commented tests

* Revert gdb test change

* Update csharp descriptor.

* Add test for empty php_namespace.

This fixes a compiler bug that caused a Java syntax error when one .proto file
would import another one with an empty package and java_package. This fixes
issue #3114.

* not to use std::random_device for map.Seed().

* remove include random

* Comment out unused arguments.

These last few are all that's needed to compile with -Wunused-arguments.

* Fix missing struct field initializer.

With this fix, everything compiles with -Wmissing-field-initializers.

* Add support for disabling unaligned memory accesses on x86 too.

ubsan doesn't like these because they are technically undefined
behavior, so -DGOOGLE_PROTOBUF_DONT_USE_UNALIGNED will disable them easily.

* Avoid undefined integer overflow.

ubsan catches all of these.

show help if protoc is called without any arguments, pre-empts -h and --help to show a useful message instead of just 'Missing input file.'

See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=189Signed-off-by: Mario J. Rugiero <mrugiero@gmail.com>

This prevents the contents of the std namespace from being effectively
pulled into the top-level namespace in all translation units that
include common.h. I left in individual using statements for a few common
things like std::set and std::map, because it did not seem worth going
through the churn of updating the whole codebase to fix those right now.

When compiling with -Werror, -Wunused-const-variable the build fails due
to those two constants not being used.

descriptor.proto uses proto2 syntax, which is not ready for external
usage. However, some proto3 files import descriptor.proto and cannot be
used. In this PR, all references (We cheated by only removing
extensions, which is enough for now. User should avoid using messages
defined in descriptor.proto as field type.) to content in
descriptor.proto are removed from generated files. Those that import
descriptor.proto can be used like other proto files.

Fix the bug by sharing the code for generating class name for both
message and enum.

InternalDeallocate to avoid confusing the compiler when there's
a class named Element already defined in the global namespace.

* Use PyUnicode_AsEncodedString() instead of PyUnicode_AsEncodedObject()

* Cherrypick the fix descriptor_pool.FindFileContainingSymbol by extensions.

See https://github.com/google/protobuf/issues/2425

* Issue #2211: Addressing GCC warning on enumeral/non-enumeral in conditional expression.

* Updated per 80 character wrap.

arm-nacl-clang seems to produce a mysterious compiler error when it
encounters __builtin_clzll, so when we are building for NaCl, let's
avoid that in favor of the portable implementation of
Log2FloorNonZero64.

This option will be prepended to generated classes of all messages in
the containing file.