Fix building on mingw32

* src/gcrypt-int.h: Include <types.h>.

'ulong' is not defined on W32, so we need to include "types.h" in
'gcrypt-int.h'.

In file included from ../src/visibility.h:53:0,

from ../src/g10lib.h:39,
from compat.c:22:

../src/gcrypt-int.h:365:49: error: unknown type name 'ulong'

• Signed-off-by: Jussi Kivilinna <jussi.kivilinna@iki.fi>