Patch from Mark Wooding: stop setting GTK_EXPAND for the x-direction

on labels in tables. The effect is that if you resize (e.g.) Solo's
configuration panel, the labels to the left of the various input
boxes will remain just big enough to fit their text in, and all the
extra space will be taken up by the useful part, i.e. the input
boxes themselves. Previously the labels and input boxes would expand
in a 1:1 ratio, causing lots of space to the right of the label text
that wasn't used for anything.

[originally from svn r8599]