Some strings are surrounded by single quotes

[AntoineTurmel]

In songbird.dtd some strings are surrounded by single quotes while the rest of file uses double quotes.

See:

• https://github.com/nightingale-media-player/nightingale-l10n/blob/master/locales/en-US/songbird/songbird.dtd#L549
• https://github.com/nightingale-media-player/nightingale-l10n/blob/master/locales/en-US/songbird/songbird.dtd#L553
• https://github.com/nightingale-media-player/nightingale-l10n/blob/master/locales/en-US/songbird/songbird.dtd#L465

[rsjtdrjgfuzkfg]

Just as for #24 I'd propose some regex magic... see commit b008666 - that script solved that issues for me (locally, I did not commit the string changes).

[AntoineTurmel]

Manually fixed in 2adf0e9 to avoid big diff.
If someday POTI reopen SVB access we may do a patch...