dohanginghead() for more section openings, in particular NH, NH or NH, IP.

Reference: /n/sources/patch/applied/ms2html-heads
Date: Thu Jan 26 09:58:48 CET 2012
Signed-off-by: yarikos@gmail.com

--- /sys/src/cmd/ms2html.c	Thu Jan 26 09:56:25 2012
+++ /sys/src/cmd/ms2html.c	Thu Jan 26 09:56:18 2012
@@ -1461,6 +1461,7 @@
 void
 g_IP(int argc, char **argv)
 {
+	dohanginghead();
 	switch(list){
 	default:
 		closel();
@@ -1603,6 +1604,7 @@
 	closel();
 	closefont();
 
+	dohanginghead();
 	dohangingcenter();
 	if(argc == 1)
 		level = 0;