Bump version number to 3.5.2

Update version number to 3.5.1.1

Merge pull request protocolbuffers#4073 from pherl/changelog

Update changelog for 3.5.1

Add release log

Merge pull request protocolbuffers#3868 from pherl/3.5.x

Support win32 long path for cross compiled build

Merge pull request protocolbuffers#3642 from pherl/3.4.x

Bump version for minor release

Merge pull request protocolbuffers#3495 from pherl/c++11

Add std::forward and std::move autoconf check

Merge pull request protocolbuffers#3485 from pherl/mingw

Fix build on MinGW32

Make code free of missing-field-initializers warnings

Merge pull request protocolbuffers#3461 from TeBoring/3.4.x

Merge master into 3.4.x