m4.include/mc-cflags.m4: report real compiler in MC_CHECK_ONE_CFLAG instead of 'gcc'

Example use: CC=clang ./configure

Before the patch configure reported 'gcc' is being used:

    checking whether gcc accepts -Wcomment... yes
    checking whether gcc accepts -Wdeclaration-after-statement... yes
    checking whether gcc accepts -Wfloat-equal... yes
    checking whether gcc accepts -Wformat... yes

(config.log used proper ${CC})

After the patch it lies a bit less:

    checking whether clang accepts -Wcomment... yes
    checking whether clang accepts -Wdeclaration-after-statement... yes
    checking whether clang accepts -Wfloat-equal... yes
    checking whether clang accepts -Wformat... yes

Reported-by: Agostino Sarubbo <ago@gentoo.org>
Gentoo-bug: http://bugs.gentoo.org/449752
Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>

m4.include/mc-cflags.m4

@@ -9,7 +9,7 @@ dnl @copyright Free Software Foundation, Inc.
 
 AC_DEFUN([MC_CHECK_ONE_CFLAG],[
 
-  AC_MSG_CHECKING([whether gcc accepts $1])
+  AC_MSG_CHECKING([whether ${CC} accepts $1])
 
   safe_CFLAGS=$CFLAGS
   CFLAGS="$1"