support setting empty values (sanely) & removing support for

support setting empty values (sanely) & removing support for
space-gapping: '-o option= value'

That is a very old feature (straight from 1998), but it is super
surprising if you try setting empty values and instead get error
messages or a non-empty value as the next parameter is treated as the
value – which could have been empty, so if for some reason you need a
compatible way of setting an empty value try: '-o option="" ""'.

I can only guess that the idea was to support '-o option value', but we
survived 17 years without it, we will do fine in the future I guess.

Similar is the case for '-t= testing' even through '-t testing' existed
before and the code even tried to detect mistakes like '-t= -b' … all
gone now.

Technically that is as its removing a feature replacing it with another
a major interface break. In practice I really hope for my and their
sanity that nobody was using this; but if for some reaon you do: Remove
the space and be done.

I found the patch and the bugreport actually only after the fact, but
its reassuring that others are puzzled by this as well and hence a
thanks is in perfect order here as the patch is practical identical
[expect that this one here adds tests and other bonus items].

Thanks: Daniel Hartwig for initial patch.
Closes: 693092