Was a threading issue, uiIdle() being called from 2 threads.
Fixes #418
Fixes #227

This buffer is used for the UI thread, which runs slower than RT.
The buffer can fill very quickly, and it's only cleared during
the main thread.
So, increase this buffer in a reasonable amount to compensate.

This allows to run the new LSP plugin UIs.

Closes #409

Fixes #396

Should help #377 a little

This helps #387, but rule is defined by the plugin.
Later on the user must be able to choose the scale mode
(among other things)

Closes #345

Fixes #367

Having GPLv3 as license makes carla itself GPLv3.
Let's keep Carla at GPLv2+ please :)
(a single simple plugin is not worth the "upgrade")

Fixes #337

Fixes #344