Regular Update V1.37: performance improvements and bug fixes

Regular update V1.37

Resolved the issue that the framerate drops severely in the menu view when all sets are unlocked.
The hint system for variants [P] and combinational variants with [P] should be much faster for larger boards now (thanks to xxuurruuii for suggesting the optimization)
Fixed several issues in the game credits (thanks to Fermata4)
Fixed a bug that pressing enter during a pop-up message sometimes crashes the game