Use tde_l10n_prepare_xml macro instead of extractrc script #10

Because the new macro tde_l10n_prepare_xml provides the same extraction of strings, only in a way other than the extractrc script, there is the option to replace the extractrc script with the macro tde_l10n_prepare_xml.

The advantage is that xgettext will then generate location information corresponding directly to rows in the original XML file.

For interest: For multiple line strings, extractrc generates a location information, that points to the last line of text, while with the tde_10n_prepare_xml macro is generated location information, that points to the first line of text.

looks good. I like the fact that the reference points to the first line instead of the last line 👍

Note0: For this PR, it is required that #9 be already merged.

Note1: If you want to test #8, #9 and #10 together, there are two small conflicts between #8 and #10, because #10 removes some of the parts that were changed in #8.