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_test.cc b/src/class_linker_test.cc
index 4f94e50..eb18280 100644
--- a/src/class_linker_test.cc
+++ b/src/class_linker_test.cc
@@ -641,9 +641,9 @@
 
 TEST_F(ClassLinkerTest, FindClass_Primitives) {
   const std::string expected("BCDFIJSZV");
-  for (int ch = 0; ch < 255; ch++) {
-    char* s = reinterpret_cast<char*>(&ch);
-    const std::string descriptor(s, 1);
+  for (int ch = 1; ch < 256; ++ch) {
+    std::string descriptor;
+    descriptor.push_back(ch);
     if (expected.find(ch) == std::string::npos) {
       AssertNonExistentClass(descriptor);
     } else {