the old approach, just waiting for time to expire is not so smart, and likely not
to deal well with dodgy hardware or emulation.  wait for thr empty instead of
waiting for a certain amount of time.

Reference: /n/atom/patch/applied/pcipluartout
Date: Thu Nov  5 05:07:28 CET 2015
Signed-off-by: quanstro@quanstro.net

--- /sys/src/boot/pcipl/sub.c	Thu Nov  5 05:05:38 2015
+++ /sys/src/boot/pcipl/sub.c	Thu Nov  5 05:05:39 2015
@@ -73,8 +73,13 @@
 void
 uartputc(int c)
 {
-	outb(0x3f8 + 0, c);
-	usleep(78);
+	int i;
+
+	for(i = 0; i < 78; i++)
+		if(inb(0x3f8 + 5) & 0x20){
+			outb(0x3f8 + 0, c);
+			return;
+		}
 }
 
 void