made a number of improvements to clockmenu
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- fixed bug where clockmenu_update would trigger clock even in fullscreen mode (Alt+b), did this
  by removing clockmenu_update from .xinitrc and added commands to dwm source code
- eliminated clock flicker when updating time by implementing double buffering
- renamed clockmenu_update to clock-update so its pid would not be confused with clockmenu
  when grepping for the clockmenu ps id. Otherwise clockmenu_update would find its own pid
  and terminate itself.
- changed clockmenu date from space padded to zero padded
- added stlarch fontset to clockmenu config.h, added clock icon next to time