[mprotect.m4] Fix "warning: AC_LANG_CONFTEST" by proper quoting.

[[Imported from SVN: r7030]]

m4/mprotect.m4

@@ -7,7 +7,7 @@ AC_DEFUN([DUNE_SYS_MPROTECT],[
   AC_CHECK_HEADER(sys/mman.h,
     AC_DEFINE(HAVE_SYS_MMAN_H, 1,
                         [Define to 1 if you have <sys/mman.h>.])
-    AC_COMPILE_IFELSE(AC_LANG_PROGRAM([#include <sys/mman.h>],[mprotect(0,0,PROT_NONE);]),
+    AC_COMPILE_IFELSE([AC_LANG_PROGRAM([#include <sys/mman.h>],[mprotect(0,0,PROT_NONE);])],
       [AC_DEFINE(HAVE_MPROTECT, 1,
                         [Define to 1 if you have the symbol mprotect.])]))
   AC_LANG_POP()