Split ".org" into ".arstart" and ".arend" (address range start/end).
Address range ends are now shown in the code list view, and the
pseudo-op can be edited in app settings. Address range starts are
now shown after notes and long comments, rather than before, which
brings the on-screen display in sync with generated code.
Reworked the address range editor UI to include the new features.
The implementation is fully broken.
More changes to the AddressMap API, putting the resolved region length
into a separate ActualLength field. Added FindRegion(). Renamed
some things.
Code generation changed slightly: the blank line before a region-end
line now comes after it, and ACME's "} ;!pseudopc" is now just "}".
This required minor updates to some of the regression test results.
