INSTALL: append /usr/X11R6/include and /usr/X11R6/include/freetype2 to
X11 headers detection, so that enable fontsrv build on OpenBSD.

Change-Id: I2f3f766339a9f8beed647dfbb19a588d1825732a
Reviewed-on: https://plan9port-review.googlesource.com/1290
Reviewed-by: Russ Cox <rsc@google.com>
diff --git a/INSTALL b/INSTALL
index 31c069d..8f123b8 100755
--- a/INSTALL
+++ b/INSTALL
@@ -128,7 +128,8 @@
 if [ `uname` != Darwin ]; then
 	# Determine whether fontsrv X11 files are available.
 	rm -f a.out
-	gcc -o a.out -c -Iinclude -I/usr/include -I/usr/local/include -I/usr/include/freetype2 -I/usr/local/include/freetype2 src/cmd/fontsrv/x11.c >/dev/null 2>&1
+	gcc -o a.out -c -Iinclude -I/usr/include -I/usr/local/include -I/usr/include/freetype2 -I/usr/local/include/freetype2 \
+	    -I/usr/X11R6/include -I/usr/X11R6/include/freetype2 src/cmd/fontsrv/x11.c >/dev/null 2>&1
 	if [ -f a.out ]; then
 		echo "	fontsrv dependencies found."
 		echo "FONTSRV=fontsrv" >>$PLAN9/config