Merge pull request #963 from lakkatv/lakka

(Lakka) Handles cores that support no games
Use setting_data_get_string_representation
lakka: Remove unused variables
Merge pull request #964 from lioncash/unused

lakka: Remove unused variables
(Griffin) Add menu_lakka_backend.c to Griffin
lakka: Fix a few bugs

- Previously it would attempt to print the pointer, not the actual value in a few sprintf statements.
- Change integer to unsigned_integer for the %u sprintf call.
- Initialize jj to zero so that it doesn't get used uninitialized.
Merge pull request #965 from lioncash/unused

lakka: Fix a few bugs
(OSX) Add HAVE_LAKKA to OSX solution
(Lakka) First subitem bugfix
(Lakka) Use setting_data_get_string_representation