Avoid conflicts with stdlib.

src/lib9/lrand.c

@@ -49,7 +49,7 @@ isrand(long seed)
 }
 
 void
-srand(long seed)
+p9srand(long seed)
 {
 	lock(&lk);
 	isrand(seed);

src/lib9/rand.c

@@ -1,8 +1,7 @@
 #include	<lib9.h>
 
 int
-rand(void)
+p9rand(void)
 {
 	return lrand() & 0x7fff;
 }
-