Add WASM Support

[codehz]

hmm, just cut down all thread usage when targeting to wasm(or disabled threading feature) (including go and in expression

[bvssvni]

To fix the build and the compiler warning:

• In Cargo.toml, add "rand" to default
• In lib.rs, at line 623, use use std::thread::self; (remove JoinHandle as it is redundant)
• In runtime/mod.rs, at line 85, inherit the Send trait pub trait ModuleResolver: Send
• In runtime/mod.rs, at line 994, add module_resolver: Box::new(FileModuleResolver),
• In runtime/mod.rs, at line 2910, add #[cfg(all(not(target_family = "wasm"), feature = "threading"))]
• In lib.rs, add #[cfg(all(not(target_family = "wasm"), feature = "threading"))] to bench_push_in/bench_push_link_go/bench_threads_go
• In tests/lib.rs, add #[cfg(feature = "file")] to test_error/test_functions/test_typechk/test_syntax

[bvssvni]

I have an idea for improving the design of ModuleResolver, but this can be done in another PR. The idea is to use a function pointer instead of trait, which means we can get rid of the Box<dyn ModuleResolver>, which when not optimized by the compiler produces an extra allocation (FileModuleResolver has size 0, so it should be optimized away).

[bvssvni]

I think using feature on lifetime::Kind is going too far, as it duplicates some code that is hard to maintain.

• In lifetime/kind.rs, remove #[cfg(all(not(target_family = "wasm"), feature = "threading"))] at line 85/103/196/215
• In lifetime/node.rs, fix the match branches at line 193

[bvssvni]

I also have an idea of using empty type pattern in ast/mod.rs, but this can be done in another PR.

[bvssvni]

I'll merge this and make the changes in another PR.

Merging.

[bvssvni]

Thanks!