build,w32: Fix build on Windows.
* Makefile.am: Add EXEEXT. * secmem/secmem.c [HAVE_MMAP] (pool_is_mmapped): Only enabled with HAVE_MMAP. (init_pool): The variable PGSIZE is only used with HAVE_MMAP.
- GnuPG-bug-id: T5893
- Reported-by: Eli Zaretskii
- Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>