Audit fixes

Fixes the following audit messages:

urweb:
 * Don't use postgresql as a dependency. We allow non-Homebrew
postgresql installations.
 * Don't use mysql as a dependency. We allow non-Homebrew
mysql installations.

qt:
 * Don't use mysql as a dependency. We allow non-Homebrew
mysql installations.

Doesn't fix the following false positives:

spell:
 * Define method "aspell_available_languages" in the class body, not at the top-level

auctex:
 * Use build instead of ARGV to check options
 * Use new-style option definitions

imagemagick:
 * libtool dependency should be "depends_on 'libtool' => :build"

libp11:
 * libtool dependency should be "depends_on 'libtool' => :build"

paps:
 * Don't need to interpolate "utf8" with system

proof-general:
 * Use build instead of ARGV to check options

skytools:
 * Don't use postgresql as a dependency. We allow non-Homebrew
postgresql installations.