Proposal to remove PCRE support

[John Johansen]

I would like to propose that we remove support for PCRE based policy
from the parser/policy loader.

The last version of AppArmor to use PCRE based policy was AppArmor 2.0.1,
which was approximately 3 years ago.  The PCRE part of the code has not
been actively maintain and I doubt that it has been tested in the last
1.5 years.  Dropping PCRE support will also help in the efforts to
cleanup the parsers code base.