added several comments to rtree.h
added several comments to rtree.h

ocelot-inc/tarantool,guard163/tarantool,vasilenkomike/tarantool,nvoron23/tarantool,mejedi/tarantool,condor-the-bird/tarantool,rtsisyk/tarantool,KlonD90/tarantool,KlonD90/tarantool,KlonD90/tarantool,nvoron23/tarantool,ocelot-inc/tarantool,condor-the-bird/tarantool,guard163/tarantool,dkorolev/tarantool,mejedi/tarantool,rtsisyk/tarantool,condor-the-bird/tarantool,condor-the-bird/tarantool,dkorolev/tarantool,guard163/tarantool,Sannis/tarantool,dkorolev/tarantool,Sannis/tarantool,dkorolev/tarantool,ocelot-inc/tarantool,guard163/tarantool,Sannis/tarantool,condor-the-bird/tarantool,ocelot-inc/tarantool,vasilenkomike/tarantool,vasilenkomike/tarantool,vasilenkomike/tarantool,guard163/tarantool,dkorolev/tarantool,Sannis/tarantool,rtsisyk/tarantool,nvoron23/tarantool,nvoron23/tarantool,KlonD90/tarantool,nvoron23/tarantool,vasilenkomike/tarantool,mejedi/tarantool,mejedi/tarantool,KlonD90/tarantool,rtsisyk/tarantool,Sannis/tarantool,nvoron23/tarantool