Version section was getting confused to the API's availability,
even though it was the version the doc was genereated.
So moving it into the footer and added @SINCE@ field in the data.
The previous documentation for FcCharSetFirstPage and
FcCharSetNextPage was technically accurate, but a bit terse. I've
added an example using the returned page (root code point) and map to
give folks something concrete to work with. I've also documented
FC_CHARSET_DONE, which wasn't mentioned at all before.
To only work on writable charsets. Also, return a bool indicating whether
the merge changed the charset.
Also changes the implementation of FcCharSetMerge and FcCharSetIsSubset