[tex-live] texlive install overwrites /usr/bin/man

[Karl Berry]

          rm -f man && \

    Removes $bindir/man or e.g. /usr/bin/man

I changed texk/texlive/linked_scripts/Makefile.am to create the `man'
link only if it is a link already or nonexistent.  Also, skipped the
link creation if TL_INSTALL_OMIT_MAN_LINK is set in the environment.

I can imagine other things to do, but hopefully that will suffice.

Best,
karl