Don't use '-' in option string to getopt().

Don't use '-' in option string to getopt().

@dram reported a build failure in FreeBSD at
https://github.com/davidgiven/ack/issues/1#issuecomment-273668299

Linux manual for getopt(3) says:
> If the first character of optstring is '-', then each nonoption
> argv-element is handled as if it were the argument of an option with
> character code 1....
>
> The use of '+' and '-' in optstring is a GNU extension.

GNU/Linux and OpenBSD handle '-' in this special way, but FreeBSD
seems not to.  If '-' is not special, then em_ego can't find its input
file, so the build must fail.  This commit stops using '-' in both
em_b and em_ego, but doesn't change mcg.

Also fix em_ego -O3 to not act like -O4.