This change implements unary operator evaluation, including prefix/postfix
assignment operators. Doing this required implementing l-values properly
in the interpreter; namely, load location and dereference, when used in an
l-value position, result in a pointer to the location, while otherwise they
(implicitly, in load location's case) deference the location and yield a value.
This change looks up the main module from a package, and that module's
entrypoint, when performing evaluation. In any case, the arguments are
validated and bound to the resulting function's parameters.
This change eliminates all traces of the old, legacy errors and warnings.
It also renumbers everything so that we don't have any "gaps". Finally,
it introduces a factory method for new errors and warnings, private to
this package, that ensures we don't accidentally register duplicate IDs.
This change adds support for function calls. We do not yet wire it
into the various function call expressions, however, that should be
relatively trivial after this change. (It is dependent on figuring
out the runtime representation of load location objects and subsequent
uses of them). This change also updates the scoping logic to respect
"activation frame" style of lexical scoping, where an inner function
as a result of a call should not have access to the callee context.
This change also includes logic to detect unhandled exceptions and to
print an error as a result. Eventually, we will want stack traces here.
