Fixes #472

Fixes high cpu usage with gtk2-suil hosts

This is very useful for carla-single

Fixes a small issue mentioned in #471

Closes #479

Closes #477

Closes #473

Fixes #438

Closes #444

Closes #441

Closes #445

Only clamp outputs if plugin includes supportsStrictBounds feature,
and an output port does not set hasStrictBounds.
That case means the plugin needs strict bounds support from the host,
and does not set bounds for a port.

In the case of an output port with hasStrictBounds,
it's considered an error if the value is not really in bounds.
We won't check for this though (err, moo moo...).

Fixes #383

Fixes #402