Fix aclocal warnings:
/usr/share/aclocal/libmcrypt.m4:17: warning: underquoted definition of AM_PATH_LIBMCRYPT
--- libmcrypt-2.5.7/lib/libmcrypt.m4
+++ libmcrypt-2.5.7/lib/libmcrypt.m4
@@ -16,3 +16,3 @@
 dnl
-AC_DEFUN(AM_PATH_LIBMCRYPT,
+AC_DEFUN([AM_PATH_LIBMCRYPT],
 [dnl