Expose multiple Grand Prix, cup and round queue related structs to Lua.

(Almost) all variables in the following structs are exposed to Lua:

• grandprixinfo
• roundqueue
• cupheader_t
• gprank_t
• gprank_level_t
• gprank_level_perplayer_t
• roundentry_t

No variables can be set, only get functions work. Can be tested with this script from JugadorXEI, with edits by me to test cup get and roundqueue functionality. Use cvar gpdebug to toggle between displays for grandprixinfo (1), its current cup data (2), and rank data (3); use whatsdacupnum and whatsdacupname to find cups by id number and name respectively; and use whatsdaround to get current roundqueue information: gptest.lua

Should now finally be be ready for review, with thanks to JugadorXEI for testing and input on cleaning up the initial draft.