harmonize grep, occur and compile

[Matzi Kratzi]

grep, occur and compile all enables the user to jump to postions in
files or buffers. Occur has the ability to stay in the *occur*-buffer
while showing the occurence point is at using
occur-mode-display-occurrence. The line is centered in the buffer that
occured was started from.

It would be nice if this line could be highlighted as compile use to do.

This way the user can do a broad occur and then walk around in the
resulting buffer and cherrypick lines that he is interested in. It
will the be easy to find this line in its original context.

Thanks for emacs anyway.