Start parallelizing dex2oat.

This is enough to perform type resolution and verification in parallel.

There appears to be a bug in InitCpu --- if you start enough threads
at once, the CHECK at the end starts to fail, with self_check == NULL; I've
commented it out for now, but this will cause test failures until it's fixed.

Change-Id: I4919682520bc01d3262c6b3d00c7bd2c2860a52e
diff --git a/src/class_linker.cc b/src/class_linker.cc
index f343ed4..6f1e5aa 100644
--- a/src/class_linker.cc
+++ b/src/class_linker.cc
@@ -1881,6 +1881,8 @@
 #endif
 
 void ClassLinker::VerifyClass(Class* klass) {
+  ObjectLock lock(klass);
+
   // TODO: assert that the monitor on the Class is held
   if (klass->IsVerified()) {
     return;