Disable compilation of some files

include/grpc/support/port_platform.h

src/core/iomgr/endpoint_pair_posix.c

src/core/iomgr/fd_posix.c

src/core/iomgr/pollset.h

src/core/iomgr/pollset_kick.h

src/core/iomgr/pollset_kick_posix.c

src/core/iomgr/pollset_kick_windows.h

src/core/iomgr/pollset_posix.c

src/core/iomgr/pollset_windows.c

src/core/iomgr/pollset_windows.h

vsprojects/vs2013/grpc_unsecure.vcxproj