Blender Git Loki

Cleanup: use 'const' arguments in transform calculation

Use const arguments to simplify further optimizations.

Transforming elements shouldn't need to change their containers
data-structures.
ElementResize for grease pencil stroke thickness was
modifying TransInfo.num & TransInfo.values_final.

Now copies are operated on to preserve const correctness although
it's worth investigating if this can be avoided altogether.