Add function marks and size indications

Add a macro to annotate function end and start using both ENTRY and END
for each function. This allows valgrind (and presumably other debugging
tools) to use the debug symbols to trace the functions.

Change-Id: I5f09cef8e22fb356eb6f5cee952b031e567599b6
diff --git a/libc/arch-arm/bionic/kill.S b/libc/arch-arm/bionic/kill.S
index 2954091..33dfc2b 100644
--- a/libc/arch-arm/bionic/kill.S
+++ b/libc/arch-arm/bionic/kill.S
@@ -33,17 +33,13 @@
    of a corrupted malloc heap).
 */
 #include <sys/linux-syscalls.h>
+#include <machine/asm.h>
 
 #ifndef __NR_kill
 #define __NR_kill   37
 #endif
 
-    .text
-    .type kill, #function
-    .globl kill
-    .align 4
-
-kill:
+ENTRY(kill)
     stmfd   sp!, {r4-r7, ip, lr}
     ldr     r7, =__NR_kill
     swi     #0
@@ -51,3 +47,4 @@
     movs    r0, r0
     bxpl    lr
     b       __set_syscall_errno
+END(kill)