Add an OpenAFS config file parser

Add an OpenAFS config file parser

This adds a Kerberos INI style config file parser to OpenAFS, using
the parser contained in Heimdal as a base. Currently, it only exports
a very small number of functions, but exporting further functions is
simply a matter of adding additional shims to hide the Kerberos
context and other specifics.

Note that we don't want to just use the parser as a library because
firstly, we don't want OpenAFS to have a Kerberos dependency (as
other crypto mechanisms will, and do, exist). Secondly, MIT and
Heimdal use a different API here, so we would have to shim anyway.
Also, our own parser means that we don't need to worry about passing
in the krb5 context, and all of the issues that that presents.

Change-Id: Ic0a5ddf03266c454827c6505d5f6ffefcddd2614
Reviewed-on: http://gerrit.openafs.org/1935
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>