closes #474

This reverts commit e99747f6.

Apparently some internal JuMP logic depends on the bridges, preventing e.g.
single-variable objective functions from working with GLPK (and maybe other
solvers). Dodging that is easy, e.g. you can use `@objective(m, Max, x+0)`
instead of one that contains just `x`, but kludges like this should not be
required in the code.

(we do not use them at all, which is likely gonna hold for some time)

Closes #419

Closes #375

Miroslav Kratochvil authored 3 years ago and Miroslav Kratochvil committed 3 years ago

I needed to clean up some extra code. Notably, set_bound functions didn't have
the warning ! attached. That got me reeeeeeeaally confused.

Former-commit-id: dafa10d7

This reverts commit ac7e2fe6.