Windows port: Fix crash using fmod() on Windows 32 bit. This generates an
instruction which doesn't seem to be supported, probably need compiler-rt
for this but I couldn't get it working, so now it's compiled as a function.

Relevant LLVM bug reports:
http://llvm.org/bugs/show_bug.cgi?id=5053
http://llvm.org/bugs/show_bug.cgi?id=5052