Reverse dependencies for rsdl

Latest version of the following gems require rsdl

Gem	Version	Date	Downloads
dxruby_sdl +53.3 Thousand Downloads	`0.0.17` October 29, 2018	October 29, 2018	53.3 Thousand
dl-tetris +9.79 Thousand Downloads	`0.0.2` December 21, 2010	December 21, 2010	9.79 Thousand
app-racket +6.2 Thousand Downloads	`0.1.0` December 14, 2011	December 14, 2011	6.2 Thousand
stylet +4.59 Thousand Downloads	`0.0.2` July 28, 2018	July 28, 2018	4.59 Thousand