* add the IntegerLiteralInst + the Builder function to create it
* add Value.nonDebugUses
* add a general utility Sequence.isEmpty
* add PassContext.replaceAllUses
* add a function to erase all `debug_value` uses in PassContext.erase
* ApplySite.arguments
* BasicBlock != operator
* some Function argument related properties
* Operand.isTypeDependent
* Type.isTrivial
* bridging of raw_ostream::write
And add `UnaryInstruction` which adds a property `operand` to all unary instructions.
This replaces the existing single-operand properties, which simplifies the code.
This is the initial version of a buildable SIL definition in libswift.
It defines an initial set of SIL classes, like Function, BasicBlock, Instruction, Argument, and a few instruction classes.
The interface between C++ and SIL is a bridging layer, implemented in C.
It contains all the required bridging data structures used to access various SIL data structures.
