fix vnc-tls compilation with newer versions of GNU-TLS
tlmu:fixed makefile for tlmu-doc.html generation
tlmu:fix SDL multithreading bug by temporary add '-nographic'

issue description:
  [xcb] Unknown request in queue while dequeuing
  [xcb] Most likely this is a multi-threaded client and XInitThreads has
  not been called
  [xcb] Aborting, sorry about that.
  ../../src/xcb_io.c:178: dequeue_pending_request: Assertion
  `!xcb_xlib_unknown_req_in_deq' failed. Aborted