Documentation and simplification of some mergeinfo functions.
Documentation and simplification of some mergeinfo functions.

Patch by: me
          pburba

* subversion/libsvn_subr/mergeinfo.c
  (combine_ranges): Improve the doc string.
  (combine_with_lastrange): Substantially rewrite the doc string, in
    particular adding an overview. Remove the "lastrange" parameter as it
    was functionally redundant. Constify "new_range" as it is an input.
    Rename "revlist" to "rangelist" as that is the de facto name for
    rangelists.
  (svn_rangelist_merge, rangelist_intersect_or_remove): Adjust callers of
    combine_with_lastrange() to do without the "lastrange" parameter.

jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion