Allow JNI AttachCurrentThread to fail if not enough stack.

Add unit tests and move JavaVM JNI tests into there own set of gtests.
Bug: 18330119

Change-Id: I0e93dff783b1f5d787b3084d24122883e14951a1
diff --git a/build/Android.gtest.mk b/build/Android.gtest.mk
index 0259fb4..8753868 100644
--- a/build/Android.gtest.mk
+++ b/build/Android.gtest.mk
@@ -113,6 +113,7 @@
   runtime/instruction_set_test.cc \
   runtime/intern_table_test.cc \
   runtime/interpreter/safe_math_test.cc \
+  runtime/java_vm_ext_test.cc \
   runtime/leb128_test.cc \
   runtime/mem_map_test.cc \
   runtime/mirror/dex_cache_test.cc \