Reduce VM shutdown verbosity.

Adds -verbose:shutdown flag, defaulted to "false".  Cuts out most of the
log noise associated with shell commands.
diff --git a/vm/compiler/Compiler.c b/vm/compiler/Compiler.c
index dfcd88f..9ed3a05 100644
--- a/vm/compiler/Compiler.c
+++ b/vm/compiler/Compiler.c
@@ -468,7 +468,8 @@
      */
     dvmChangeStatus(NULL, THREAD_RUNNING);
 
-    LOGD("Compiler thread shutting down\n");
+    if (gDvm.verboseShutdown)
+        LOGD("Compiler thread shutting down\n");
     return NULL;
 }
 
@@ -508,7 +509,7 @@
 
         if (pthread_join(gDvmJit.compilerHandle, &threadReturn) != 0)
             LOGW("Compiler thread join failed\n");
-        else
+        else if (gDvm.verboseShutdown)
             LOGD("Compiler thread has shut down\n");
     }
 }