add a "const" to fix build, should fix problem seen on Dragonfly

bulk build

audio/bmpx/distinfo

@@ -1,4 +1,4 @@
-$NetBSD: distinfo,v 1.8 2007/11/01 22:49:14 tnn Exp $
+$NetBSD: distinfo,v 1.9 2007/12/08 14:42:51 drochner Exp $
 
 SHA1 (bmpx-0.40.13.tar.bz2) = 3327baa8f13f8411a15ebafd0112b9ba8623c0ef
 RMD160 (bmpx-0.40.13.tar.bz2) = 6eab5edf1ffce8c7226db59281c79c2165886d05
@@ -6,3 +6,4 @@ Size (bmpx-0.40.13.tar.bz2) = 1820642 bytes
 SHA1 (patch-aa) = b2c33a87406afc09e5b2ef01400b2e738b9c9ca4
 SHA1 (patch-ab) = c4b8094e4c542eda3278af9229aa1be58dc36b18
 SHA1 (patch-ac) = 77d88acc2c74259f293dc54699a322962f50ce57
+SHA1 (patch-ad) = 1af37a064235abd5399e70f60451c51d58f91232

audio/bmpx/patches/patch-ad

@@ -0,0 +1,13 @@
+$NetBSD: patch-ad,v 1.5 2007/12/08 14:42:51 drochner Exp $
+
+--- src/sanity.cc.orig	2007-12-08 15:29:18.000000000 +0100
++++ src/sanity.cc
+@@ -69,7 +69,7 @@ sanity_check_glib_msg (void)
+ }
+ 
+ C_FUNCTION
+-gchar *
++const gchar *
+ sanity_check_gtk (void)
+ {
+   return gtk_check_version (GTK_REQUIRED_MAJOR_VER,