Native build system for gl-docs. Removes last dependency

on imake in xenocara.

doc/gl-docs/Makefile.inc

@@ -0,0 +1,28 @@
+# $OpenBSD: Makefile.inc,v 1.1 2012/08/07 21:10:35 matthieu Exp $
+
+all:
+
+cleandir:
+
+.SUFFIXES: .3 .3gl
+
+.for page source in $(MAN)
+_INST_MAN = ${DESTDIR}${MANDIR}$(page:E)/$(page:T)
+${_INST_MAN}: ${source}
+	${INSTALL} ${INSTALL_COPY} -o ${MANOWN} -g ${MANGRP} -m ${MANMODE} \
+	  ${.ALLSRC} ${.TARGET}
+
+install: ${_INST_MAN}
+
+.PHONY: ${_INST_MAN}
+.endfor
+
+install:
+.for lnk file in $(LINKS)
+	@l=${DESTDIR}${MANDIR}${lnk:E}/${lnk}; \
+	t=${DESTDIR}${MANDIR}${file:E}/${file}; \
+	echo $$t -\> $$l; \
+	rm -f $$t; ln $$l $$t;
+.endfor
+
+NOOBJ=