Output more detailed error message if loading library fails

Bug: 9805979

Change-Id: I77b19d6a65ff9fb72e7428ce79b117628e4c8658
diff --git a/media/libmediaplayerservice/SharedLibrary.h b/media/libmediaplayerservice/SharedLibrary.h
index 5353642..88451a0 100644
--- a/media/libmediaplayerservice/SharedLibrary.h
+++ b/media/libmediaplayerservice/SharedLibrary.h
@@ -29,6 +29,7 @@
 
         bool operator!() const;
         void *lookup(const char *symbol) const;
+        const char *lastError() const;
 
     private:
         void *mLibHandle;