snap restrictions (hor./vert.) are broken

[r.koebler]

When moving objects in inkscape, I can press "Ctrl" to restrict the movement to horizontal/vertical. But when the object then snaps to an other object, it completely ignores the horizontal/vertical restriction.

How to reproduce: I've attached a simple drawing with two rectangles. Open it and
- enable "Snap to paths"
- grab the green rectangle near the lower left corner
- press and hold ctrl
- move the mouse up and down -- the rectangle will move only horizontally/vertically
- move the mouse a bit to the right, and then down to the red rectangle
As soon as the lower left corner of the green rectangle snaps to the path of the red rectangle, the hor./vert. restriction is completely ignored.

This is very bad, since this means that I constanly have to create temporary guides for every restricted move, and only snap to the guides.

Tested with:
- Inkscape 0.48.3.1 r9886 (Debian Wheezy)
- Inkscape 0.48.5 r10040

It worked correctly in:
- Inkscape 0.47 r22583, built Mar 12 2010

[su_v (suv-lp)]

On S X 10.7.5:
- not reproduced with Inkscape 0.47
- reproduced with all releases in the stable 0.48.x series
- not reproduced with current trunk (0.91pre2 r13590).

Based on tests with archived trunk builds:
- reproduced with trunk rev <=9716
- not reproduced with trunk rev >= 9719
this regression seems to have been fixed in revision 9719
<http://bazaar.launchpad.net/~inkscape.dev/inkscape/trunk/revision/9719>

The fix will be included in the next major release 0.91.