Refactor DescribeVRegs to allow caching.

In oatdump we want to describe vregs at regular intervals and reverifying is
slow. Refactor MethodVerifier to allow this. Move instruction flags into its
own file so the complete type is visible to files other than method verifier.

Change-Id: I14d491e7376ab1d7117a9725847870ef1337803f
diff --git a/build/Android.common.mk b/build/Android.common.mk
index f35458c..65cb75d 100644
--- a/build/Android.common.mk
+++ b/build/Android.common.mk
@@ -258,6 +258,7 @@
 	src/utils.cc \
 	src/vector_output_stream.cc \
 	src/verifier/dex_gc_map.cc \
+	src/verifier/instruction_flags.cc \
 	src/verifier/method_verifier.cc \
 	src/verifier/reg_type.cc \
 	src/verifier/reg_type_cache.cc \