Issue 2172: Get line and column numbers right.

Issue 2172: Get line and column numbers right.

This uses 1-based columns on all error output, as is the standard for
GNU programs.  It also flags version errors as being for line 1
instead of line 0 since the latter confuses Emacs' compilation mode.

The same column convention is used for point-and-click column numbers
in textedit:// URIs.  In contrast, the byte offsets into a line (also
in those URIs) are retained 0-based.

For point-and-click, this yields the correct results when using the
definitions for emacs and gvim in scm/editor.scm, the editors
configured to interpret the column number.

It is to be expected that Lilypond-specific shells (like Frescobaldi
called via Okular for point-and-click) have specialized on the
previous wrong behavior and will now exhibit the kind of one-off
behavior that non-LilyPond specific programs did previously when
encountering the error messages.

I don't see a good migration strategy for those except possibly
looking for the version number of LilyPond and deciding whether to do
one-off calculations depending on that.

[Graham Percival, 2012-12-16 01:08:31]

could we get something in Changes.tely about this?  No need to update this
patch; you can push the modification to changse.tely immediately once this patch
is accepted.

[dak, 2012-12-16 08:15:43]

On 2012/12/16 01:08:31, Graham Percival wrote:
> could we get something in Changes.tely about this?  No need to update this
> patch; you can push the modification to changse.tely immediately once this
patch
> is accepted.

I did not do so on the theory that "bug fixes should not be mentioned in
Changes", but of course if potentially everybody using the functionality needs
to adapt to the fixed behavior, this is worth mentioning.  Will do.  I am also
not sure that fixing the (utf-8 character count based) column number in textedit
URIs to 1-based but leaving the byte offset 0-based is the right choice, but I
don't know which tools and editors actually use the byte offset.

[dak, 2012-12-16 10:47:04]

Add changelog entry