Add a bunch more missing ENDs to assembler routines.

This isn't everything; I've missed out those x86 files that are

Change-Id: Idb7bb1a68796d6c0b70ea2b5c3300e49da6c62d2
diff --git a/libc/arch-x86/string/memchr.S b/libc/arch-x86/string/memchr.S
index d6bcbe6..367c7b4 100644
--- a/libc/arch-x86/string/memchr.S
+++ b/libc/arch-x86/string/memchr.S
@@ -24,3 +24,4 @@
 L1:	xorl	%eax,%eax
 	popl	%edi
 	ret
+END(memchr)