Add tests for variables and functions. The old ones were actually for var and function refs.
Add tests for type and type-ref menus. Reference bug 1082099.
Fix menus for declarations of structs, classes, enums, functions, etc. Ref bug 1082099.

* Change the name of declloc field in decldef CSV lines to just "loc". Unlike most other kinds of lines with decllocs, decldef ones don't also have a plain old "loc". This change makes process_loc kick in and extract the loc, combine it with the extent, and make a 'span' key, so the menus get made.
* Remove the Extent-constructing line from process_defloc(). It was doing the wrong thing, putting ints rather than Positions into the Extent. Now process_loc() kicks in for decldef lines (which are the only kind with a defloc) and takes care of the extent field, turning it into a 'span' field.