Strengthen gcc-internal-format: Check that %< %>, %r %R, %{ %} come in pairs.

Strengthen gcc-internal-format: Check that %< %>, %r %R, %{ %} come in pairs.

* gettext-tools/src/format-gcc-internal.c (format_parse): New local variables
in_quote_group, in_color_group, in_url_group. Add pairing checks for %< %>,
%r %R, %{ %}.
* gettext-tools/tests/format-gcc-internal-1: Update.
* gettext-tools/tests/format-gcc-internal-2: Update.