Expand the list of errors accepted from Clang.

While here, more specific error message for unhandled defect classes, as
"unknown error" is annoyingly non-specific, and leads one to believe that
perl itself is dying.

Some whitespace fixups while here as well.
Move Vigilante to using Config::Tiny, since Config::General is ballsed for the moment.

As a benefit, the config handling logic becomes utterly simpler.
Better description for TOCTOU defect class in vigilante.sql
whitespace nits in Vigilante perl modules
Consistently use "class" instead of sometimes using "type"
when manipulating/describing defects.
Only attempt to check for skipfile matches if the skipfile has been specified
Add support for, and begin parsing, the signature skip file
Support for "action" statements in vigilante.conf; arbitrary shell
commands, with !<argument> interpolation

XXX -- needs documentation