Add some helpful custom scons tools from my personal library.

One of these is good for creating LLVM bitcode from either C or C++ code.  The other knows how to compare actual and expected file contents, and touch a ".passed" stamp file if the files match.

Use these two tools where appropriate in our testing logic.  They don't do much for us now, since we have only one test.  But they will make things more convenient as the test suite grows.
Rebuilt JSON output from iiglue.

Apparently iiglue does not add a trailing newline to its output.  We ended up with one here because I hand-edited this file at some point.  Removing it (in this commit) brings us back to what iiglue really does produce as its output.
Add an iiglue reader test for variadic functions.

To my surprise, this actually worked right from the start, requiring no IIGlueReader changes.  Cool!  Having this test should help ensure it keeps working.