Paddles bugfix

Previously, attempting to launch a game that used Paddle controllers would fail because the assertion on the line https://github.com/mdraves91/stella-libretro/blob/bugfix-p2controller/stella/input/Paddles.cpp#L225 would fail since two of the Paddles global variables were never initialized.

This commit makes sure they are initialized when a game is loaded.

You should probably accept my other pull request first because this branch came out of the other bugfix branch (whoops)