Improve <sys/cdefs.h>.

Fix and use __RENAME (and lose ___RENAME --- two underscores should be
enough for anybody). This was the point of this change, because I want
to use __RENAME to support the two basename variants and the two
strerror_r variants.

Lose a bunch of macros that weren't being used.

Lose three dead files from the DNS code.

Change-Id: I3ef645c566b16a52217bc2e68c7d54b37c7c9522
diff --git a/libc/include/string.h b/libc/include/string.h
index 8df68e3..643132d 100644
--- a/libc/include/string.h
+++ b/libc/include/string.h
@@ -180,8 +180,7 @@
     return __builtin___memset_chk(s, c, n, __bos0(s));
 }
 
-extern size_t __strlcpy_real(char* __restrict, const char* __restrict, size_t)
-    __asm__(__USER_LABEL_PREFIX__ "strlcpy");
+extern size_t __strlcpy_real(char* __restrict, const char* __restrict, size_t) __RENAME(strlcpy);
 extern size_t __strlcpy_chk(char *, const char *, size_t, size_t);
 
 __BIONIC_FORTIFY_INLINE
@@ -204,8 +203,7 @@
     return __strlcpy_chk(dest, src, size, bos);
 }
 
-extern size_t __strlcat_real(char* __restrict, const char* __restrict, size_t)
-    __asm__(__USER_LABEL_PREFIX__ "strlcat");
+extern size_t __strlcat_real(char* __restrict, const char* __restrict, size_t) __RENAME(strlcat);
 extern size_t __strlcat_chk(char* __restrict, const char* __restrict, size_t, size_t);