Fixed compilation error on mingw. Used _MSC_VER for MSVC-specific code instead of WIN32. Recieved patch from cjacek. BUG=12 Review URL: http://codereview.appspot.com/1694049 git-svn-id: https://angleproject.googlecode.com/svn/trunk@343 736b8ea6-26fd-11df-bfd4-992fa37f6226