Add fps_lock method to GameLoop and public attr fps_target

[ryukinix]

Closes #26

Set fps_target for all examples

• lerax-breakout -> 60fps
• lerax-square -> 60fps
• lerax-square-platform -> 120fps (60fps is not enough)
• wesleycsj-doom-fire -> 60fps
• wesleycsj-hello-world -> 60fps

Now the CPU consumption is very low! My CPU temp is not burning anymore.

[wesleycsj]

Ok, the functionality seems work well. The only thing, less important, is the name of the variable, i don't think which fps_target is a good name for variable, and doesn't better to it be setted in something like a set method? Like this, "game.set_max_frame_rate(60);" ?

[ryukinix]

Ok, the functionality seems work well. The only thing, less important, is the name of the variable, i don't think which fps_target is a good name for variable, and doesn't better to it be setted in something like a set method? Like this, "game.setMaxFramerate(60);" ?

Good suggestion, fps target is a common term used in various context, but of course we can change it. I think providing the method set_max_frame_rate(int) would be enough in that case.

[wesleycsj]

Ok. Don't forget to update all examples after in the same commit.