Update Ruby to the latest version.
 2.0.0p576 and 2.1.3.
Handle $CPPFLAGS properly.

RubyInstaller 2.1.3 adds __MINGW_USE_VC2005_COMPAT in CPPFLAGS.
This flag is necessary for time_t because it changes time_t to 64bit from 32bit.
Version 1.2.4.