m4-1.4.7: inconsistency in src/m4.h

[Martin Koeppe]

Hello,

in src/m4.h I found, that the test for _POSIX_VERSION should only be 
made, after unistd.h has been included. Otherwise the test should be 
omitted, as _POSIX_VERSION gets #defined in <unistd.h>.

   #include <config.h>

+  /* _POSIX_VERSION is #defined in unistd.h */
+  #if HAVE_UNISTD_H
+  #include <unistd.h>
+  #endif

   /* Canonicalize UNIX recognition macros.  */
   #if defined unix || defined __unix || defined __unix__ \
     || defined _POSIX_VERSION || defined _POSIX2_VERSION \
     || defined __NetBSD__ || defined __OpenBSD__ \
     || defined __APPLE__ || defined __APPLE_CC__
   # define UNIX 1
   #endif

Martin