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/_setjmp.S b/libc/arch-arm/bionic/_setjmp.S
index 5626219..6b8aa50 100644
--- a/libc/arch-arm/bionic/_setjmp.S
+++ b/libc/arch-arm/bionic/_setjmp.S
@@ -70,6 +70,7 @@
 
         mov	r0, #0x00000000
         bx      lr
+END(_setjmp)
 
 .L_setjmp_magic:
 	.word	_JB_MAGIC__SETJMP
@@ -109,3 +110,4 @@
 	bl	PIC_SYM(_C_LABEL(longjmperror), PLT)
 	bl	PIC_SYM(_C_LABEL(abort), PLT)
 	b	. - 8		/* Cannot get here */
+END(_longjmp)