Don't prepend "^Inst" or append a space to the "include", "exclude", or
"critical" regular expressions. Instead, check for lines beginning
with "Inst" using strncmp and apply the regular expressions only when
such lines are found.

Fixes Debian bug #522812, along the lines suggested by the bug
submitter, Justin T Pryzby.
Fix SourceForge bug 1904965 - check_apt: SECURITY_RE is not correct

For the default security upgrade detection regular expression, match
"Debian-Security" in package description when it's anywhere after the
first parenthesis (not just the second space-delimited word). For
example:

... (4.0.1-5.4 Debian:6.0.6/stable, Debian-Security:6.0/stable ...
Tests for check_apt

Add a hidden "--input-file" option to check_apt (modelled on
check_procs) so that it can take files with sample apt output as input.

Add tests for my SECURITY_RE fix (debian3) and for the include, exclude
and critical options.
Merge pull request #20 from abradley/aptcritical

Fixes for check_apt handling of -i/-e/-c regexps and SECURITY_RE, plus tests