* configure.ac: Require 2.54.

s/jm_FUNC_MALLOC/AC_FUNC_MALLOC/.
s/jm_FUNC_REALLOC/AC_FUNC_REALLOC/.
* m4/c-bs-a.m4, m4/malloc.m4, m4/mbstate_t.m4, m4/realloc.m4:
Remove, provided by Autoconf macros.

m4/realloc.m4

@@ -1,40 +0,0 @@
-#serial 6
-
-dnl From Jim Meyering.
-dnl Determine whether realloc works when both arguments are 0.
-dnl If it doesn't, arrange to use the replacement function.
-dnl
-
-AC_DEFUN([jm_FUNC_REALLOC],
-[
- dnl xmalloc.c requires that this symbol be defined so it doesn't
- dnl mistakenly use a broken realloc -- as it might if this test were omitted.
- AC_DEFINE(HAVE_DONE_WORKING_REALLOC_CHECK, 1,
-           [Define if the realloc check has been performed. ])
-
- AC_CACHE_CHECK([whether realloc(0,0) returns a non-NULL pointer],
-                jm_cv_func_working_realloc,
-  [AC_TRY_RUN([
-    char *realloc ();
-    int
-    main ()
-    {
-      exit (realloc (0, 0) ? 0 : 1);
-    }
-	  ],
-	 jm_cv_func_working_realloc=yes,
-	 jm_cv_func_working_realloc=no,
-	 dnl When crosscompiling, assume realloc(0,0) returns NULL.
-	 jm_cv_func_working_realloc=no)
-  ])
-  if test $jm_cv_func_working_realloc = yes; then
-    AC_DEFINE([HAVE_REALLOC], 1,
-	      [Define to 1 if your system has a working `realloc' function,
-	       and to 0 otherwise.])
-  else
-    AC_DEFINE([HAVE_REALLOC], 0)
-    AC_LIBOBJ(realloc)
-    AC_DEFINE(realloc, rpl_realloc,
-      [Define to rpl_realloc if the replacement function should be used.])
-  fi
-])