extensions: changed to call extsetup() from extensions.loadall()
previously uisetup() was invoked by extensions.loadall(), but
extsetup() was by _dispatch().
there's no need to split them because we have nothing to do
between uisetup() and extsetup().
this fixes
issue1824 indirectly.
%% Should show unknown
? unknown
removing b
%% Should show unknown and b removed
R b
? unknown
%% Should show a and unknown
a
unknown