Remove __overloadable/__RENAME_CLANG

Now that we have a clang that supports transparent overloads, we can
kill all of this cruft, and restore our upstream sources to their
untouched glory. Woohoo!

Bug: 12231437
Test: Built aosp_marlin; no obvious patch-related aosp_mips issues.
Change-Id: I520a19d014f12137f80e43f973dccd6711c571cd
diff --git a/libc/arch-mips/string/strchr.c b/libc/arch-mips/string/strchr.c
index c9397e7..3458f66 100644
--- a/libc/arch-mips/string/strchr.c
+++ b/libc/arch-mips/string/strchr.c
@@ -92,7 +92,7 @@
   return (char *)p;
 }
 
-char* strchr(const char* s, int c) __overloadable
+char* strchr(const char* s, int c)
 {
   const op_t *w;
   op_t mask_1, mask_128, mask_c;