0.42.16

16 Fix --back and --fore in GtkSourceView builds.

Cheat sheet about how options interplay in GtkSourceView-enabled builds

**SYNTAX HIGHLIGHT A SHELL SCRIPT file.sh**

- yad --text-view --lang=sh < file.sh
- yad --text-view --lang=sh --filename=file.sh
- yad --text-view --filename.sh

In the last line, the correct filename EXTENSION, ".sh" must be given to
get syntax highlighting.  Use --lang if the correct extension can't be
given.

Any of the above commands can also take option --theme but if neither
--lang nor --filename are given, --theme by itself is ignored.

**CHANGE TEXT BACKGROUND / FOREGROUND COLOR**

- yad --text-view --back=yellow --fore=red < file

Do not pass any of --lang or --filename otherwise yad will ignore
--back and --fore and attempt to syntax highlight the input text.