Cygwin fixes by Ben van Klinken

For fun I tried compiling strigi with cygwin. I got the core things working (deepfind, etc), here's a small patch of the things i had to change to make it work (against the current svn).

Mostly compile stuff (assumptions are made that if the compiler is not msvc then it is mingw). Also there are some ambiguous casts for addValue. And a small typo in the strigiconfig.h.cmake file (which wasn't actually necessary, but is probably incorrect).