prevent segmentation fault when requested area is too big; if select is interrupted while WriteExact, just try again.

 increase rfbMaxClientWait when threaded to avoid ReadExact() timeouts for some viewers.

 modify configure.ac to pick up -lXinerama

 -debug_pointer, and -debug_keyboard
 add reverse connections, keysym remapping,
 and debug output option

 add clipboard/selection handling.
 add visual option (mostly for testing and workarounds).
 improve shm cleanup on failures.

 improved pointer input handling during drags, etc.
 somewhat faster copy_tiles() -> copy_tiles()
 x11vnc options -buttonmap -old_pointer -old_copytile

 minimize memory usage under -nofb