Initial llvm support
Implement basic LLVM codegen
LLVM codegen produces output acceptable for llc
LLVM output now assembles and links
Refactor some instruction creation functions
Add some global declaration and initialization code
Make LLVM codegen work with C backend's declarations
Add code for calling C functions
Remove dead code
Add code for pushing/popping the stack
Rename some operations, add helper functions for making gep, load, store and alloca instructions
Use mkgep helper function
changes to getOperand, better portability for pointer arithmetic operations
Fix getOperand issues
Fix issue with array offset operands
Many fixes and completions
Modify creation of context, fix return address saving in CCall
Codegen fixes
Codegen fixes for pointer equality
Fixes for real comparisons, rotates, and undefined llvm intrinsics