Typo fixed.

m4/check-package.m4

@@ -69,7 +69,7 @@ else
 fi
 AC_ARG_WITH($1-headers,
 AC_HELP_STRING([--with-$1-headers=DIR],
-               [use $1 include files below directory DIR (default: $6)])x,
+               [use $1 include files below directory DIR (default: $6)]),
 [case "$withval" in
     yes) AC_MSG_ERROR("option \"--with-$1-headers\" requires an argument")
 	;;