windows:check for nonconforming swprintf arguments

Newer versions of mingw do include the correct API for swprintf.
Check for _CRT_NON_CONFORMING_SWPRINTFS as specified in the swprintf
documentation:
http://msdn.microsoft.com/en-us/library/ybk95axf(v=vs.90).aspx
build: include internal headers in source list

allows 'make dist-*' targets to generate working tarballs