We changed the MSRV in the last release because some dependency depended on
Rust 1.59. But that did not concern the C++ build, for example.
Now that we rely on rust 1.59 in our own code, we should make it explicit
so that the compilation error show the proper error
This avoid repeating the enums both in the compiler and in
the runtime library, and register them in a bunch of other places.
So it should be easier to add enums and enum values
Since cbindgen doesn't see through the macro, generate the enum
manually
cbindgen 0.21 was released which contains https://github.com/eqrion/cbindgen/pull/724
which allow to use raw identifier in enums shared with C++.
So now we can have `MouseCursor.move` in slint despite it being a rust keyword
Note that the strum macro also have trouble with the raw identifier, so we
take that in account in the conversion functions in the interpreter
* Build the backends without rtti unless needed
Only the interpreter needs the rtti generated code.
* Since `SlintElement` emits `#[cfg(feature = "rtti")]` tokens, each
crate using `SlintElement` needs to have an `rtti` feature.
* The selector gets backend specific rtti selection features, in order
for the interpreter to enable them.
* Enable rtti when building the C++ project with the interpreter enabled
The README.md contains the warning that used to be in lib.rs.
Add README.md files to all internal crates
... pointing to the official public crate to use instead.
Rename internal crates
fixup: README files
fixup rename
