Better player name lookups

[talvo]

When listing mail with @mail *<player>, abbreviated names of online players aren't checked (should use match_player not lookup_player)

visible_short_page can fail when there's only one player you can see whose name matches a prefix, but there's also a dark player who matches that you can't see.

[talvo]

The * arg to locate() doesn't do player name lookups without a leading *, despite saying it does everything (should include MAT_PMATCH)

[talvo]

(Since locate() has probably been that way for a decade or two, I'd actually be inclined to treat that one as a documentation bug, rather than change it and risk breaking stuff.)

[shawnw]

Fixed the help for locate() to match actual behavior. Commit aafdc16