Log Message:
Update p5-CGI to 4.28:

4.28 2016-03-14

    [ RELEASE NOTES ]
    - please see v4.21 Changes for any potentially impacting changes

    [ SPEC / BUG FIXES ]
    - undef %QUERY_PARAM in initialize_globals to clean mod_perl env

    [ TESTING ]
    - improve test coverage on request types (GH #199, GH #200)
    - improve test coverage on CGI::Carp