In keeping with the change made by @ridiculousfish earlier today modify
the `keyword_description()` function to return a const wchar_t pointer.
Also, simplify the `token_type_description()` function to use the recently
introduced mapping array. This changes the wording of many of the token
type descriptions. However, I can't see this as being a problem since
the original descriptions (e.g., "token_redirection") are no clearer to
someone not acquainted with the implementation.
Introduces a new template moved_ref which is like an rvalue reference.
This allows passing around objects while being explicit that the
receiver may acquire ownership. This will help reduce some allocations.
Rather than returning a list of productions and an index,
return the relevant production directly from the rule function.
Also introduce a tag value (replacing production_idx) which tracks
information like command decorations, etc. with more clarity.
This change moves source files into a src/ directory,
and puts object files into an obj/ directory. The Makefile
and xcode project are updated accordingly.
Fixes#1866
