For libm, use a macro for aliasing symbols.

Change-Id: Ibd42ebc387c2bf3eba9aa96091770915b4b34184
diff --git a/libm/x86/e_atan2.S b/libm/x86/e_atan2.S
index a6ad390..1efdf65 100644
--- a/libm/x86/e_atan2.S
+++ b/libm/x86/e_atan2.S
@@ -452,8 +452,7 @@
 # -- End  atan2
 
 # Start file scope ASM
-.weak atan2l
-.equ atan2l, atan2
+ALIAS_SYMBOL(atan2l, atan2);
 # End file scope ASM
 	.section .rodata, "a"
 	.align 16