malloc bug fixes.

use malloc by default.
free stacks.

R=r
DELTA=424  (333 added, 29 deleted, 62 changed)
OCL=21553
CL=21584
diff --git a/src/runtime/mem.c b/src/runtime/mem.c
index 0db941e..8e7a472 100644
--- a/src/runtime/mem.c
+++ b/src/runtime/mem.c
@@ -23,17 +23,6 @@
 	MAP_ANON	= 0x1000,	// not on Linux - TODO(rsc)
 };
 
-void*
-stackalloc(uint32 n)
-{
-	return mal(n);
-}
-
-void
-stackfree(void*)
-{
-}
-
 // Convenient wrapper around mmap.
 static void*
 brk(uint32 n)
@@ -51,7 +40,7 @@
 // right here?"  The answer is yes unless we're in the middle of
 // editing the malloc state in m->mem.
 void*
-mal(uint32 n)
+oldmal(uint32 n)
 {
 	byte* v;