* Add support for calling vararg functions (must pass doubles in int regs too)

* Make visitSetCondInst() share condition-generating code with EmitComparison()
* There are 13 FPRs for function-passing arguments, not 8
* Do not rely on registers being sequential, use an array lookup
* In unimplemented switch cases, send an error and abort instead of silent
  fall-through
* Add doInitialization() for adding function prototypes for external math fns
* Minor changes: fix indentation, spacing, code clarity

llvm-svn: 14653