- Texture allocation in constructor didn't initialize data so caused glitches as soon as the picktoolbar appeared.
-> Textures are now created AND initialized on demand (at first selection update).

- The texture for knot selection mode didn't display the right selection intervals.

- Replaced texture mode GL_MODULATE by GL_REPLACE in order for the curve selection areas to appear brighter and thus more visible.

git-svn-id: http://www.openflipper.org/svnrepo/OpenFlipper/branches/Free@11150 383ad7c9-94d9-4d36-a494-682f7c89f535