Collada: Added ngon support to Vertex Color exporter

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@55020 954f8c5b-7b00-dc11-b283-0030488c597c
Fix #34475: Weird noise bug with Texture nodes

Made Texture compositor input node single-threaded since
texture trees are not thread-safe.

Also fixed texture being flipped horizontally and vertically.
Why nobody noticed this for 3 releases already??

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@55021 954f8c5b-7b00-dc11-b283-0030488c597c