Handle kb by treating it as a backspace. Make pangox rendering the

Handle kb by treating it as a backspace. Make pangox rendering the

* src/vte.c: Handle kb by treating it as a backspace.  Make pangox
  rendering the default.  Handle control-key sequences better, unless
  the input method is hiding the modifiers from us.  Set the default
  TERM variable to "xterm-color".
* src/vte.c src/vte.h: Get rid of vte_terminal_set_core_font().