The first two patches is a necessary refactoring. There, filePosition was a file-specific opaque struct fpos_t, whereas the actual concept was simply an offset of the tag in current file.
The 3-rd patch fixes bug #7 (closed). The refactoring is needed for the fix because parser is written in Vala, and there doesn't seem to be any standard way to convert fpos_t to an index (in fact, Vala doesn't even support that type).