Merge changes from topic 'bionic_unavailable'

* changes:
  Tag unavailable functions with macro.
  Delete declarations which don't exist.
diff --git a/libc/Android.mk b/libc/Android.mk
index 02682af..374ffa6 100644
--- a/libc/Android.mk
+++ b/libc/Android.mk
@@ -589,11 +589,6 @@
 
 use_clang := true
 
-# b/25291096, Clang/llvm compiled libc.so for mips/mips64 failed to boot.
-ifeq ($(TARGET_ARCH),$(filter $(TARGET_ARCH),mips mips64))
-  use_clang := false
-endif
-
 # Try to catch typical 32-bit assumptions that break with 64-bit pointers.
 libc_common_cflags += \
     -Werror=pointer-to-int-cast \