Make window resizable

[bregma]

The game window is currently fixed at "80 columns by 25 rows of text" which on today's modern hardware is pretty teeny tiny. With the switch away from using curses-on-console to exclusively using PDCurses on libSDL2, dynamic window sizing can be supported.

Two high-level goals need to be met to accomplish this change.

• Explicitly set up the SDL surface before initializing curses, so the SDL_Surface is under game control
• Modify almost every line of output code to reference the dynamic window size instead of using an implicitly hard-coded 80x25 value.