[vim] Improve typealias and associatedtype

[tokorom]

Update only utils/vim/syntax/swift.vim

Improve the syntax highlight for typealias and associatedtype.

Problematic patterns

Expects

[compnerd]

Please keep the list of keywords sorted.

[compnerd]

Should we not highlight associatedtype as a keyword rather than a type identifier? I guess you can argue either way.

[tokorom]

I read Declarations of Swift Language References and thought typealias and associatedtype to be close. That's because both typealias and associatedtype has typealias-name immediately afterwards.

That is a reason I moved associatedtype to swiftTypeDefinition.

• Type Alias Declaration

typealias-declaration → attributes access-level-modifier typealias typealias-name generic-parameter-clause typealias-assignment

• Protocol Associated Type Declaration

protocol-associated-type-declaration → attributes access-level-modifier associatedtype typealias-name type-inheritance-clause typealias-assignment generic-where-clause