Macros for symbols used in both ASM and C

-The macros take care of prepending the leading underscore when
 necessary.

lib/libc/arch/i386/string/strcmp.S

@@ -4,9 +4,8 @@
 /* int strcmp(const char *s1, const char *s2) */
 /*	Compare two strings. */
 /* */
-.text
-.globl	_strcmp
-.balign	16
-_strcmp:
+#include <machine/asm.h>
+
+ENTRY(strcmp)
 	movl	$-1, %ecx	/* Unlimited length */
-	jmp	__strncmp	/* Common code */
+	jmp	_C_LABEL(_strncmp) /* Common code */