* First draft of TrapSink implementation.
* Add trap sink calls to 'trapif' and 'trapff' recipes.
* Add SourceLoc to trap sink calls, and add trap sink calls to all loads and stores.
* Add IntegerDivisionByZero trap to div recipe.
* Only emit load/store traps if 'notrap' flag is not set on the instruction.
* Update filetest machinery to add new trap sink functionality.
* Update filetests to include traps in output.
* Add a few more trap outputs to filetests.
* Add trap output to CLI tool.
This allows us to run the tests via a library call rather than just
as a command execution. And, it's a step toward a broader goal, which
is to keep the code in the top-level src directory minimal, with
important functionality exposed as crates.
