Fix build with gcc-3.4.

Submitted by:	roam

lang/mit-scheme/files/patch-uxio.c

@@ -0,0 +1,14 @@
+
+$FreeBSD$
+
+--- uxio.c.orig	Tue Apr  3 19:51:52 2001
++++ uxio.c	Thu Aug  5 00:40:16 2004
+@@ -236,7 +236,7 @@
+   return ((scr < 0) ? 0 : scr);
+ }
+ 
+-#ifdef _POSIX
++#ifdef __FreeBSD__
+ #include <string.h>
+ #else
+ extern int EXFUN (strlen, (CONST char *));