Clean up reentrancy cruft.

The DNS copy of reentrant.h was unused, so remove it.

The strtod implementation can use the upstream-netbsd reentrant.h and
get a little closer to what was then upstream. (It's since been replaced
by gdtoa, and we'll have to follow at some point, but for now this doesn't
make anything any worse.)

ANDROID_CHANGES is (now) only used in the DNS code, so push the -D
down.

The <locale.h> change prevents an LP32 hack from leaking into LP64.

Change-Id: Idf30b98a59d7ca8f7c6cd6d07020b512057911ef
diff --git a/libc/Android.mk b/libc/Android.mk
index 056efd2..8cb85b7 100644
--- a/libc/Android.mk
+++ b/libc/Android.mk
@@ -400,7 +400,6 @@
 # Define some common cflags
 # ========================================================
 libc_common_cflags := \
-    -DANDROID_CHANGES \
     -D_LIBC=1 \
     -Wall -Wextra \
 
@@ -513,6 +512,7 @@
 LOCAL_SRC_FILES := $(call all-c-files-under,dns)
 LOCAL_CFLAGS := \
     $(libc_common_cflags) \
+    -DANDROID_CHANGES \
     -DINET6 \
     -I$(LOCAL_PATH)/dns/include \
     -I$(LOCAL_PATH)/private \