Target: add support to build CallLoweringInfo

Rather than introducing an auxiliary CallLoweringInfoBuilder, add the methods to
do chained function construction directly to CallLoweringInfo.  This reduces the
monstrous 15-parameter constructor into a series of simpler (for some definition
of simpler) functions that control particular aspects of the call.  The old
interfaces can be completely removed once callers are moved to the new chained
constructor pattern.

llvm-svn: 209081