Automatic commit by arc
leanup: style, use 'const' where possible, and simplified blend funcs.

Much better to use small loops when doing complex operations over color elements
(any serious compiler will flatten them anyway), avoids (some!) stupid mistakes when
editing their code.

Also, use min/max funcs instead of lengthier 'if (foo < 0) foo = 0'.
Cleanup: general cleanup in BLI_math code (mostly, use 'const' where possible, true/false for booleans, format for float litterals).
Fix addon crash when trying listdir a directory we have no permission to.
Code cleanup, make pie-menus code be closer to master
Fix T41241: VSE: cropping strips puts a transparent line through the image.
BLI_path_utils: rename BLI_clean -> BLI_path_native_slash
initial intersect code
initial isect
intersection script
test vert intersection
check for intersections where no new verts are added first
minor fixes
WIP
add vert-edge check
Print info
De-duplicate - dont add same verts to edge multiple times
Dissolve
Dissolve based on tags
improve intersection dissolve