Fix class_linker_test now FindClass uses const char*.

Also move FindSystemClass into the .cc file, where it belongs.

Change-Id: I171555ad6cf408be926b3f99ea61e2c5a835d1ec
diff --git a/src/class_linker.cc b/src/class_linker.cc
index 4d3b2ea..5a3887a 100644
--- a/src/class_linker.cc
+++ b/src/class_linker.cc
@@ -993,6 +993,10 @@
   return klass;
 }
 
+Class* ClassLinker::FindSystemClass(const char* descriptor) {
+  return FindClass(descriptor, NULL);
+}
+
 Class* ClassLinker::FindClass(const char* descriptor, const ClassLoader* class_loader) {
   DCHECK(*descriptor != '\0') << "descriptor is empty string";
   Thread* self = Thread::Current();