This change adds a new Review Bot tool to run clang --analyze.
Setting up clang properly requires some configuration. In particular, the

static analyzer needs the compiler to be able to run successfully (though not

the linker), so the user may need to add a bunch of import paths or other

configuration to the command line. I've facilitated this by including a setting

for additional command-line arguments, which is split with shlex and then

appended to the clang command line.
Clang is the first tool that can actually report multiple lines per comment.

I've fixed up the review functionality to properly translate the line numbers

for this.

Connected the git repository to my local Review Board, configured it in the

Review Bot worker, and then used the post-commit UI to create review requests

for a bunch of different commits. Most of them are pretty clean, but saw that

in a few cases, the clang static analyzer ran successfully and reported the

bugs.