Patch fixes typo in configure script and prevents removing $(srcdir) from
VPATH in Makefile.

Also, fixes build on hurd-i386, kfreebsd-i386 and kfreebsd-amd64
architectures.

--- memchan-2.3.orig/configure
+++ memchan-2.3/configure
@@ -8793,7 +8793,7 @@
 fi
 
 	    ;;
-	Linux*)
+	Linux*|GNU*)
 	    SHLIB_CFLAGS="-fPIC"
 	    SHLIB_SUFFIX=".so"
 
@@ -11704,7 +11704,6 @@
 # (actually we leave an empty line to preserve line numbers).
 if test "x$srcdir" = x.; then
   ac_vpsub='/^[	 ]*VPATH[	 ]*=/{
-s/:*\$(srcdir):*/:/
 s/:*\${srcdir}:*/:/
 s/:*@srcdir@:*/:/
 s/^\([^=]*=[	 ]*\):*/\1/