Implementation of open_memstream().

POSIX seems to have chosen open_memstream() over the BSD variant.  We
want something for Dalvik that will work on both GNU/Linux and Android,
so this is open_memstream() implemented in terms of BSD funopen().

For Windows there's just a stub that calls abort().

I'm putting this in libcutils since it seems inappropriate for bionic
(which provides the BSD alternatives) but isn't Dalvik-specific.
diff --git a/libcutils/Android.mk b/libcutils/Android.mk
index b219473..93933e2 100644
--- a/libcutils/Android.mk
+++ b/libcutils/Android.mk
@@ -31,6 +31,7 @@
 	config_utils.c \
 	cpu_info.c \
 	load_file.c \
+	open_memstream.c \
 	strdup16to8.c \
 	strdup8to16.c \
 	record_stream.c \