This quotes with default options of the specified style,
but with quoting enabled for instances of ':'.
While this can be simulated by temporarily modifying
the default quoting style, this is a little awkward,
and care must be taken with such an implementation
to avoid inlining leading to bloated text.
* lib/quotearg.h (quotearg_n_style_colon): Description and declaration.
* lib/quotearg.c (quotearg_n_style_colon): New function implementation.