Switch back to LOCAL_CLANG with -std=gnu89.

The root issue here is that Clang was defaulting to gnu99, which has different
semantics for inline functions (that are not in fact bugs). Switching back to
gnu89 (like gcc was defaulting to) resolves the link problem.

Change-Id: I4fa786aff18ef3f435f83b4a5f1a3ee9dc039432
diff --git a/Android.mk b/Android.mk
index 77ed0e2..de76dd6 100644
--- a/Android.mk
+++ b/Android.mk
@@ -22,7 +22,7 @@
 	pngwtran.c \
 	pngwutil.c
 
-common_CFLAGS := -fvisibility=hidden ## -fomit-frame-pointer
+common_CFLAGS := -std=gnu89 -fvisibility=hidden ## -fomit-frame-pointer
 
 ifeq ($(HOST_OS),windows)
   ifeq ($(USE_MINGW),)
@@ -59,7 +59,7 @@
 # =====================================================
 
 include $(CLEAR_VARS)
-# LOCAL_CLANG := true
+LOCAL_CLANG := true
 LOCAL_SRC_FILES := $(common_SRC_FILES)
 LOCAL_CFLAGS += $(common_CFLAGS) -ftrapv
 LOCAL_C_INCLUDES += $(common_C_INCLUDES) \