create an X Input Method in obt for the app to use for all input
() -> (void) also in .h files, and fix a place that gave arguments when it shouldn't have.
make an obt_root() macro
add prop.[ch] to the libobt, but they are not used yet. add a global obt_display which obt can use, and the application.
move the code for tracking what extensions are available on the display into the libobt
move the xerror handling into the libobt
Move the main loop out into the libobt