Envelope: <> return path now always matches as the empty string, regardless of the specified address part.

Imapflags: resolved problem of hasflags encountering duplicate flags in flag lists contained in a variable.

Resolved code duplication among commands that use comparators and match-types and found problems in the imapflags extension in the process.

Significantly improved handling of old/corrupt binaries and revised matching implementation in the process.

Working towards improving the handling of currupt binaries: defined multiple exit codes for execution functions and defined trace macro for reporting binary corruptions.

Fixed code emission for extension-defined variables and removed hardcoded paths from include extension.

Testsuite: tested handling of teststuite envelope environment and fixed bugs in the envelope test in the process.

Reversed stat() and open() on two occasions to make retrieved stat information guaranteed to be valid for the opened file and added error handling for various close() system calls.