For libm, use a macro for aliasing symbols.

Change-Id: Ibd42ebc387c2bf3eba9aa96091770915b4b34184
diff --git a/libm/arm/s_floor.S b/libm/arm/s_floor.S
index 4405358..3af8f76 100644
--- a/libm/arm/s_floor.S
+++ b/libm/arm/s_floor.S
@@ -136,7 +136,4 @@
 
 END(floor)
 
-#if LDBL_MANT_DIG == 53
-        .weak           floorl
-        .equ            floorl,floor
-#endif
+ALIAS_SYMBOL(floorl, floor);