FileGenerator::GenerateBuildDescriptors() emits
"::google::protobuf::internal::OnShutdown(&$shutdownfilename$);" which is
declared in common.h.

Although Protobuf is very well tested a compilation error was triggered while
rolling Protobuf r423:426. There might be something wrong in the Chromium roll
(still in progress).

It seems safer anyway not to rely on indirect headers inclusion.

This does additionally a significant cleanup in platform_macros.h (initially
pulled from v8).
It implemented some subtleties that we don't use like the HOST/TARGET arch
distinction.

Changes related to NaCl support come from Chromium's build/build_config.h.

BUG=392

Fix license headers.

This patch makes the generation of StaticDescriptorInitializer_$filename$
depend on whether LITE_RUNTIME is enabled. Note that this works only when
extensions are not used.

This lets us significantly decrease the number of static initializers generated
by protoc in LITE_RUNTIME mode (used in Chromium).
In LITE_RUNTIME mode, $adddescriptorsname$() is called the first time that
default_instance() is called (rather than being called during static init).

To benefit from this patch in LITE_RUNTIME mode without extensions, compile
with -DGOOGLE_PROTOBUF_NO_STATIC_INIT.

BUG=351

It is based on V8's new CallOnce(): http://codereview.chromium.org/9447052/.

This patch includes the following changes:
  - POD (no static initializer generated) and faster implementation on Windows.
  - GoogleOnceInit() can now take an additional parameter which is forwarded to
    the function provided by the user.

This patch is part of the static initializers removal initiative.

which affects proto compiler in generating field has_bit mask.

setup.py to fix RPATH problem.