package/autoconf: hardcode m4 config

Hardcode m4 config instead of letting configure detect it automatically.
This hopefully fixes the build issues some (Ubuntu) users seems to be
having lately (E.G. #679).

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>
diff --git a/CHANGES b/CHANGES
index 1452823..6e5eef3 100644
--- a/CHANGES
+++ b/CHANGES
@@ -2,8 +2,8 @@
 
 	Additional fixes and cleanups.
 
-	Updated/fixed packages: alsamixergui, coreutils, fltk, microperl,
-	ncurses, vim
+	Updated/fixed packages: alsamixergui, autoconf, coreutils, fltk,
+	microperl, ncurses, vim
 
 	Issues resolved (http://bugs.uclibc.org):