Update constants completions from official source code

[p4t5h3]

The constants shipped with PureBasic are available in its open-source repository.

This would be great to automate so it is easy to update this package with future releases of PureBasic.

[tajmone]

This would be great to automate so it is easy to update this package with future releases of PureBasic.

In theory yes, in practice not really since the PB repository doesn't use tagged releases, so it's impossible to track changes across different PB releases (see: fantaisie-software/purebasic#143).

Being able to pin-point to which PB version the sources refer to would be extremely useful in order to keep the package consistent with each PB version, especially now that we're on the verb of a MAJOR version bump in PureBasic.