Server: Use nanosleep() instead of POSIX-obsolete usleep() in io.c.

[plomrogue] / TODO

Next planned steps in plomrogue development:

BOTH SERVER/CLIENT:

- make server and client communicate by specific world state info requests 
  in server/out, replacing server/worldstate

- check for return values of *printf()

- be more strict and humble when allocating memory from the stack

SERVER:

- implement field of view / line of sight and obstacles for those on the map

- is it actually useful to define map object action ids in the config file?

- for game continuation, replace re-playing of whole record files with loading
  game state snapshots / save files

CLIENT:

- enable toggling of window borders

- make log scrollable