corrections to modifiers from recent normal handling changes
- solidify didn't define a dependsOnNormals callback (which it should have)
- build wasn't passing on dirty normals.
- decimate wasnt setting dirty normals.


git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@57188 954f8c5b-7b00-dc11-b283-0030488c597c