[Bf-committers] new patch#18645 adding more texture paint blending modes

[Fredrik hansson]

http://projects.blender.org/tracker/?func=detail&aid=18645&group_id=9&atid=125

this adds the following blending modes:
overlay
hard light
color burn
linear burn
color dodge
screen
soft light
pin light
vivid light
linear light
difference
exclusion
hue
saturation
luminosity
color

did only write these for unsigned char textures so they won't work with floating point textures

and i had some issues with rgb_to_hsv + hsv_to_rgb causing crashes due to what im guessing is the threading so i made new versions of those functions to not use any pointers.

compiled against rev:26834