+ some fixes to clipper offset methods, and additional controls over the number of vertices at round joins
#rb david.hill
#preflight 6430d1e7b306e98c639e68a8
[CL 24984017 by jimmy andrews in ue5-main branch]
also:
Update polygon union code to allow the input array to be (optionally) re-used as the result array
Fix the previous offset function to support negative offsets for polygons
#rb ryan.schmidt
#preflight 63f7f9b12b1a2765f9210b37
[CL 24397851 by jimmy andrews in ue5-main branch]