sljit/sljitExecAllocator.c: use MAP_ANON

sljit/sljitExecAllocator.c: use MAP_ANON

With the PCRE-8.44 release, sljitExecAllocator.c started testing
to see if it can successfully mmap a PROT_WRITE + PROT_EXEC block
of memory before adding the MAP_JIT flag.

Unfortunately, unlike the rest of the code, the addition uses
MAP_ANONYMOUS for that mapping rather than MAP_ANON.

The file sljitUtils.c is included before sljitExecAllocator.c and
is very careful to make sure that if MAP_ANON is NOT defined, but
MAP_ANONYMOUS is, then it defines MAP_ANON to be MAP_ANONYMOUS.

However, it *does not* do the reverse and on MacOSX systems that
have a MAP_ANON definition, but *not* a MAP_ANONYMOUS definition,
that new sljitExecAllocator.c code fails to compile.

Change sljitExecAllocator.c to use MAP_ANON instead of MAP_ANONYMOUS
to correct the problem.

Signed-off-by: Kyle J. McKay <mackyle@gmail.com>