is testing the bitcode reader's functionality, not VMCore's. Add the
what is a hope sufficient build system mojo to build and run a new
unittest.

Also clean up some of the test's naming. The goal for the file should be
to unittest the Bitcode Reader, and this is just one particular test
among potentially many in the future. Also, reverse my position and
relegate the PR# to a comment, but stash the comment on the same line as
the test name so it doesn't get lost. This makes the code more
self-documenting hopefully w/o losing track of the PR number.

llvm-svn: 147431