[cairo] Adding to_string() functions for all enums.

[Jeff Smith]

 Behdad wrote:
> While working on the cairocairo probe (a tool to output cairo calls an
> app makes), I figured it should be useful for bindings of all kinds to
> have to_string() functions for all cairo enum types.  One that prints
> out the name of the enum value.  The problem is, we already have
> cairo_status_to_string() that unfortunately /describes/ the error, not
> just writing out the status name.  So, at least for that one the name
> to_string() cannot be used.  Suggestions on alternate names?  Unless

If you're still open to suggestions, you might consider _as_string()

 -- Jeff Smith