memchr.c breaks with some warnings turned on

[Monty Taylor]

memchr.c doesn't compile if -Wunused-macros -Werror is turned on. Also,
just looking at #if HAVE_BP_SYM_H also throws warnings which make
-Werror builds die.

=== modified file 'gl/memchr.c'
--- gl/memchr.c 2008-10-15 23:04:53 +0000
+++ gl/memchr.c 2008-10-16 20:27:53 +0000
@@ -39,10 +39,12 @@

 #include <limits.h>

-#if HAVE_BP_SYM_H || defined _LIBC
+#if defined(HAVE_BP_SYM_H) || defined _LIBC
 # include <bp-sym.h>
 #else
-# define BP_SYM(sym) sym
+# ifdef weak_alias
+#  define BP_SYM(sym) sym
+# endif
 #endif

 #undef __memchr