Envelope: fixed bug in application of address parts; failure to obtain the part would cause inappropriate match success (bug reported by Ron Lee)

Testsuite: added RFC compliance tests for the variables extension and fixed use of wrong default comparator.

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

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.

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

Properly implemented dumping a binary including a list of required extensions and support for extension-specific output.

Implemented support for overriding default argument implementations of number, string and string-list.

Added support for reading an entire stringlist into memory. Also fixed various identical bugs in stringlist-related error handling.