Improve compiler string shown in version()

With some compilers such as Clang and ICC emulating GCC, using a
version string of the form "GCC $version" can be quite misleading.
Also, a great while ago, the version output from gcc --version started
including the string "gcc", so it is redundant to repeat that.  In
order to support ancient GCC versions, we now prefix the result with
"GCC " only if the version output does not start with a letter.

configure

@@ -29704,7 +29704,8 @@ $as_echo "$as_me: using LDFLAGS=$LDFLAGS" >&6;}
 
 # Create compiler version string
 if test x"$GCC" = x"yes" ; then
-  cc_string="GCC `${CC} --version | sed q`"
+  cc_string=`${CC} --version | sed q`
+  case $cc_string in [A-Za-z]*) ;; *) cc_string="GCC $cc_string";; esac
 elif test x"$SUN_STUDIO_CC" = x"yes" ; then
   cc_string=`${CC} -V 2>&1 | sed q`
 else

configure.in

@@ -1849,7 +1849,8 @@ AC_MSG_NOTICE([using LDFLAGS=$LDFLAGS])
 
 # Create compiler version string
 if test x"$GCC" = x"yes" ; then
-  cc_string="GCC `${CC} --version | sed q`"
+  cc_string=`${CC} --version | sed q`
+  case $cc_string in [[A-Za-z]]*) ;; *) cc_string="GCC $cc_string";; esac
 elif test x"$SUN_STUDIO_CC" = x"yes" ; then
   cc_string=`${CC} -V 2>&1 | sed q`
 else