Modify Code to Work with Clang/C++11

Merge from widevine repo of http://go/wvgerrit/15659

The clang compiler is more strict about C++11. This is needed for
future Android work.

In particular, iostream no longer converts to bool automtically, so
those instances were replaced with ss.fail().

Arrays or structures that appear to be variable length need to be
placed last in a structure.  In oemcrypto_test a variable size
structure was replaced with an explicit buffer size, and a check was
added to make sure the buffer is not exceeded.

bug: 20893039
Change-Id: I5e25fc618dcf68262079c15554ee4ceae1858b8b

libwvdrmengine/oemcrypto/test/Android.mk

@@ -2,8 +2,6 @@ LOCAL_PATH:= $(call my-dir)
 
 include $(CLEAR_VARS)
 
-LOCAL_CLANG := false
-
 LOCAL_MODULE:=oemcrypto_test
 LOCAL_MODULE_TAGS := tests