gEDA: Gschem: right mouse button-> hierarchy menu

[sdb-at-NOSPAMcloud9_dot_net (Stuart Brorson)]

Hi Guys --

I've always wanted to have the ability to push down into a symbol from
the right mouse button.  I'm used to it from ViewDraw, I guess.
Therefore, I just added that capability to gschem, and just uploaded
it to CVS.

I also made the hierarchy menu items sensitive, meaning that they are
greyed out if you don't have anything selected.  The sensitivity is 
coarse-grained right now.  That means that if you select a normal
symbol, then "Down Schematic" is also highlighted, just like in the
top menu bar.  Maybe someday I'll improve that. . . . .

Please try it out next to you synch up with CVS, and let me know if
you have success using it.  Complaints/bug reports to me, as always.

Stuart