Fix bug with a1176080

If you pass a symbol here, it will be interpreted as the name of a
face to use. This works correctly if you use the symbol highlight,
which is the name of a face, or if you define a face called
browse-kill-ring-inserted-item-face. However, a new user will not have
such a face defined (since we don't define it) and will notice
that (even if she sets browse-kill-ring-highlight-current-entry) the
current entry won't be highlight. A similar bug exists for
browse-kill-ring-highlight-inserted-item.
Fix bug with highlighting inserted item

791330f7 introduced a bug by removing a redefinition of the variable
pt. pt as passed in is the value of point in the Kill Ring buffer; it
bears no relationship whatsoever to the value we want, which is the
value of point in the buffer we're inserting into.

Make this a little clearer by using a new name for the variable. This
requires a reindent.
Document the previous fix
Add browse-kill-ring-replace-yank

I'm very used to yank-pop replacing what I just yanked if it wasn't
what I wanted. This brings that behavior to browse-kill-ring.

This might cause puzzling behaviors if you yank something and then
want to yank something else using browse-kill-ring immediately
afterwards. However, it seems that most users of browse-kill-ring
either replace C-y (yank) with browse-kill-ring, or enhance
M-y (yank-pop) without replacing it by using
browse-kill-ring-default-keybindings, so we should be safe to enable
this behavior by default.
goto-char as the last thing in a save-excursion is never right
Refactor do-prepend-insert, do-append-insert, and do-insert into one function

791330f7 did some simplification, which was later improved upon by
88077ef4, to browse-kill-ring-do-insert. Sibling functions
browse-kill-ring-do-prepend-insert and
browse-kill-ring-do-append-insert were left untouched. Since these
functions are basically just copies of each other, refactor the shared
parts into a shared function, browse-kill-ring-insert-and-highlight.
Merge pull request #6 from glasserc/master

misc fixes and browse-kill-ring-replace-yank