Autoconf tweaks: Use the HAVE_MMAP in wordlist.c. Enable fork for any
system that pass AC_FUNC_FORK.
Add AX_LANG_COMPILER_MS inlined in configure.ac (it was replaced
in the GNU archive by a more generic macro, but I don't want to
hack ax_opencl.m4).
Use -O0 during feature tests. Using -O2 is begging for trouble.
Add missing header for exit(3) in most autoconf AC_LANG_SOURCE tests.
Add a separate test for -march=native, closing #583. Also drop remains
of obsoleted JOHN_CFLAGS et al.
added size checking for all common elemental data types. Changed the ARCH_INT_GT_32 check to use this information
Revert changes to makefile
Try to ignore Makefile in src, by explictly specifying that one
src/Makefile as a true file (cp Makefile.orig Makefile).  Trying to get rid of git seeing Makefile, even though it is in .gitignore
added config.cache to .gitignore, and set Makefile back to a ln -s.  NOT SURE HOW to fix Makefile to have something there, BUT be ignored
Hack workaround for Makefile vs. .gitignore
moved x86 special logic into a macro. PUtting this into macro cleans up configure.ac, AND it makes it much easier to start adding logic for other systems, and then within configure.ac, simply have a switch on the system type, to call the right one.   Also, moved the ax_lang_compilerr_ms into a macro to clean house a bit, and a few other small cleanups
Conditionally include some standard -L and -I directories.
Fix MPI check. AC_PROG_CC_MPI replaces AC_PROG_CC so we must not run
the latter first.
Remove obsoleted stuff from para-best.pl
Fix X32 build. There were several issues but nothing major - except maybe
we can't add '-m32' or '-m64' from configure. That sort of thing must be
left to the user.

./configure CFLAGS=-mx32 ASFLAGS=-mx32 LDFLAGS=-mx32 --disable-mpi
Add shorthand "--with-arch=opt" which adds opt to CFLAGS, ASFLAGS and
LDFLAGS. The best example might be "--with-arch=-m32" altough many other
uses are possible.

Do not enable MPI automatically, because users might be scared by
personal firewalls complaining about "network activity".

Add --disable-nss option. This might be needed for cross compiling since
pkg-check is not suitable for that.
AC_USE_SYSTEM_EXTENSIONS must be run *after* MPI test, otherwise the
latter is screwed.
Fix for "light" cross-compile (eg. X32 or 32-bit, on a 64-bit host).
We must preserve CFLAGS but if we put -O0 in its tail, we override
any -O2 that come before it.

Also, ditch the AC_USE_SYSTEM_EXTENSIONS macro. It's not compatible
with AX_PROG_CC_MPI at all. We currently handle such extensions in
os.h so we don't really need it right now.
Autoconf: Portability fix. Note to self: Always exit() from main in configure
tests, never return. Do not include <stdlib.h> but define "extern void exit(int);"
instead. This is portable while not producing garbage in config.log.