Add some extra debugging/diagnostic support.

CHECK that we don't bring a class back from a "permanent" error status in the
oat file at runtime.

CHECK that runtime_support.cc doesn't hand out 0 as an address for its caller
to branch to.

Also remove some accidentally left in debugging output.

Also fix a few comment typos.

Change-Id: Ibf4224940e9013184888c7854e675b17e0500ac9
diff --git a/src/runtime_support.cc b/src/runtime_support.cc
index b002c5c..af8ce22 100644
--- a/src/runtime_support.cc
+++ b/src/runtime_support.cc
@@ -1013,6 +1013,9 @@
   DCHECK(!self->IsExceptionPending());
   const void* code = method->GetCode();
 
+  // When we return, the caller will branch to this address, so it had better not be 0!
+  CHECK(code != NULL) << PrettyMethod(method);
+
   uint32_t method_uint = reinterpret_cast<uint32_t>(method);
   uint64_t code_uint = reinterpret_cast<uint32_t>(code);
   uint64_t result = ((code_uint << 32) | method_uint);