w32: Add a cast for GetProcAddress, add AM_CFLAGS for w32spawn.
* src/Makefile.am (gpgme_w32spawn_CFLAGS): Add AM_CFLAGS. * src/gpgme-w32spawn.c (my_spawn): GetProcAddress returns an address for the symbol. The correctness should be checked by human when writing the code (not by the function prototype).
- GnuPG-bug-id: T7968
- Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>