This should be friendlier to most users. It does, however, mean
we lose range information. However, range information could be
recovered by re-parsing, as janet's grammar is simple enough to do this.
This allows better stacktraces when manually intercepting
signals to clean up resources. Also allows functionality
from Common Lisp's unwind-protect, such as calling cleanup code
while unwindinding the stack, restarting on certain signals, and
just in general having more control over signal and signal propagation.
Also fix a bug encountered while implementing with-resource in the
compiler. Desturcturing arguments that were not the last argument
would often result in bad code generation, as slots used to destructure
the earlier arguments would invalidate the later parameters. This is
fixed by allocating all named parameters before doing any destructuring.
