Big honkin mapgen speedup: fix http://i.imgur.com/Q3i8FSr.png

speed up map::load over %1000 by using tinymap, potentially eliminating 4212 needless temporary submaps in map::generate (which resulted in 2343168+ std::vector constructor/destructors)

 before: total 626ms, generate(36): 611ms, 4356 submaps created (4212 temporary)
 now: total: 44ms, map::generate x 36: 30ms, 144 submaps created