Corrected all outstanding top-level issues.

Specifically, @{compile} now properly compiles both ordered and unordered
suboverlays. @{main} has also seen significant improvements to debug
functionality, providing new core aliases :run_line_if_debugging() and
:output_line_if_debugging(); such aliases are *GUARANTEED* to reduce to noops
under non-debug release builds of zeshy, a demonstrable improvement over the
prior method (albeit at slight usability cost).