memchr is required by ansi to treat the argument character
and the data as unsigned chars, and the extension memccpy might
as well too.  normal libc already does that.

Reference: /n/sources/patch/applied/ape-memchr
Date: Fri Sep  7 11:36:19 CES 2007
Signed-off-by: forsyth@terzarima.net

--- /sys/src/ape/lib/ap/gen/memchr.c	Fri Sep  7 11:31:36 2007
+++ /sys/src/ape/lib/ap/gen/memchr.c	Fri Sep  7 11:31:34 2007
@@ -3,9 +3,10 @@
 void*
 memchr(const void *ap, int c, size_t n)
 {
-	char *sp;
+	unsigned char *sp;
 
 	sp = ap;
+	c &= 0xFF;
 	while(n > 0) {
 		if(*sp++ == c)
 			return sp-1;
--- /sys/src/ape/lib/ap/gen/memccpy.c	Fri Sep  7 11:31:53 2007
+++ /sys/src/ape/lib/ap/gen/memccpy.c	Fri Sep  7 11:31:50 2007
@@ -3,10 +3,11 @@
 void*
 memccpy(void *a1, void *a2, int c, size_t n)
 {
-	char *s1, *s2;
+	unsigned char *s1, *s2;
 
 	s1 = a1;
 	s2 = a2;
+	c &= 0xFF;
 	while(n > 0) {
 		if((*s1++ = *s2++) == c)
 			return s1;