when working on the profiling i noticed, not for the first time,
that getpid calls memset to clear the whole buffer, but only the
first byte needs to be cleared, which can easily be done directly.

Notes:
Mon Mar 26 21:28:54 EDT 2012 geoff
    it's not quite that simple, so i've done it differently.


Reference: /n/sources/patch/sorry/getpid-less-memset
Date: Tue Mar 27 01:07:59 CES 2012
Signed-off-by: forsyth@terzarima.net
Reviewed-by: geoff

--- /sys/src/libc/9sys/getpid.c	Tue Mar 27 01:07:00 2012
+++ /sys/src/libc/9sys/getpid.c	Tue Mar 27 01:06:57 2012
@@ -7,7 +7,7 @@
 	char b[20];
 	int f;
 
-	memset(b, 0, sizeof(b));
+	b[0] = 0;
 	f = open("#c/pid", 0);
 	if(f >= 0) {
 		read(f, b, sizeof(b));