Upgrading depenency on rake-compiler to latest 0.8.x.
Fixing a typo/bug in the windows cross-compile rbconfig-1.9.3 DLDFLAGS check.
Experimental support for cross-compiling for ruby 2.0 on windows.
Merge branch 'windows-ruby-2.0-support'
Version bump to 1.5.7.rc3, plus changelog update.