Add a few more complex-related cast kinds that arise due to arbitrary

Add a few more complex-related cast kinds that arise due to arbitrary
implicit conversions;  the last batch was specific to promotions.
I think this is the full set we need.  I do think dividing the cast
kinds into floating and integral is probably a good idea.

Annotate a *lot* more C casts with useful cast kinds.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@119036 91177308-0d34-0410-b5e6-96231b3b80d8