Change casts from old style to new style. This helps document the details

Change casts from old style to new style. This helps document the details
better, gives the compiler a chance to validate the cast and reduces warnings
if the user turns on -Wold-style-cast option.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@41033 91177308-0d34-0410-b5e6-96231b3b80d8