Fix underquoting.

https://sourceforge.net/p/aa-project/bugs/12/
https://sourceforge.net/p/aa-project/patches/5/
https://sourceforge.net/p/aa-project/support-requests/5/
--- aalib.m4.orig	2008-03-11 12:48:25.000000000 -0400
+++ aalib.m4	2008-03-11 12:48:34.000000000 -0400
@@ -9,7 +9,7 @@
 dnl AM_PATH_AALIB([MINIMUM-VERSION, [ACTION-IF-FOUND [, ACTION-IF-NOT-FOUND]]])
 dnl Test for AALIB, and define AALIB_CFLAGS and AALIB_LIBS
 dnl
-AC_DEFUN(AM_PATH_AALIB,
+AC_DEFUN([AM_PATH_AALIB],
 [dnl 
 dnl Get the cflags and libraries from the aalib-config script
 dnl