new 'showvers' option

Add options 'showvers' (boolean) and 'versinfo' (numeric mask) to
show nethack's version on the status lines during play.  It won't be
particularly interesting to ordinary players but should be useful
when making screenshots or video to be streamed, or for someone who
switches between git branches or between nethack and variants.

I worked on this several months back but it was combined with
unfinished changes to 'hitpointbar'.  I've separated it out so that
it can be put into use.  When enabled, one or more components of
"<name> <branch> <version>" will be shown right justified after
status conditions.  At present the default is "<branch>" if that is
available and overall status isn't 'released', or "<version>" if
'released' or if branch isn't available.  That might need some
refinement.

It works as intended for tty and curses, although some abbreviation
mechanism would be useful if/when the program resorts to abbreviating
status conditions to make things narrow enough to fit.

For X11, it works ok for fancy_status:True (the default, controlled
via NetHack.ad settings) but is messed up for tty-style status.  The
text is positioned correctly but there are gaps in it, making it
appear garbled, similar to what I saw when I tried and failed to
implement statuslines:3 for X11.  [It might be due to having empty
condition widgets be 1 pixel wide instead of being totally removed
but I don't think the situation is that simple.]

For Qt, if the text needs to be truncated in order to fit, the center
portion of the string will be shown, discarding parts from the left
and right.  That ought to discard from left and retain rightmost
portion instead.

For win32|mswin|Win GUI, no attempt to support it has been included.
Things should be ok when 'showvers' is left as False (the default)
but I don't know what will happen if that gets toggled to True.  At a
minimum, the version info won't be right justified.  The information,
or at least some of it, is displayed in the game window's title bar
so there isn't any pressing need to add it to status, but toggling
the option will need to behave sensibly if it doesn't already.

include/patchlevel.h

@@ -17,7 +17,7 @@
  * Incrementing EDITLEVEL can be used to force invalidation of old bones
  * and save files.
  */
-#define EDITLEVEL 97
+#define EDITLEVEL 98
 
 /*
  * Development status possibilities.