Conflicts:
	gflags-vs2003.sln
	gflags-vs2010.sln
	gflags-vs2012.sln
	vsprojects/gflags_unittest/gflags_unittest-vs2010.vcxproj
	vsprojects/libgflags/libgflags-vs2010.vcxproj

Change version to 2.1.0, i.e., use common semantic versioning system including patch number for bug fix releases.

This reverts commit fb21f3cc.

Add link dependency on shlwapi.lib during build configuration instead of #pragma comment statement. Use this library also on MinGW.

The OS_WINDOWS #define has previously been used in gflags.cc before the CMake migration.

Copied from CMake master branch.