This is a large commit, which introduces general API for working with
abstraction of Platform.
- Add new abstraction to 'core' - SimplePlatform - which represents
exactly one platform
- Clients are strongly prohibited to create instances of SimplePlatform
by hand, instead, corresponding *Platforms abstraction should be used
(e.g. JvmPlatforms, JsPlatforms, KonanPlatforms)
- Move TargetPlatform to 'core', it represents now a collection of
SimplePlatforms
- Clients are strongly encouraged to use TargetPlatform
(not SimplePlatform) in API, to enforce checks for multiplatform
- Provide a helper-extensions to work with TargetPlatform
(in particular, for getting a specific component platform)
- Remove MultiTargetPlatform in favour of TargetPlatform
- Notably, this commit leaves another widely used duplicated abstraction,
namely, IdePlatform. For the sake sanity, removal of IdePlatform is
extracted in the separate commit.
This decouples simple data (TargetPlatform) from other subsystem-specific
logic (like default imports, built-ins, etc.).
Aside from purely aesthetic improvements, it also makes it easier
to move 'TargetPlatform' into core (see next commits)
Dmitry Savvinov