Minor FreeBSD fixes put in place

From: SHIOZAKI Takehiko <takehi-s@ascii.co.jp>

I tried snapshot(Oct30) and made some patches.
# I think that it is confused to manage both Makefile.shlib and
# makefiles/Makefile.*, don't you?

* configure
        Now FreeBSD 2.X is not supported..., so I added its entry.
        If ELF_SYSTEM is set, gmake treat it defined even though
        it is "false".  So nothing should be set to use "ifdef".
        BSD_SHLIB etc. may have same problems.

* Makefile.shlib
        As you said, FreeBSD entry is much like BSD's.
        I only added ELF_SYSTEM code.

* makefiles/Makefile.freebsd
        Ifdef/else/endif can not be indented with TABs.