build: Update CocoaAsyncSocket to 7.6.4

[qmfrederik]

The copy of CocoaAsyncSocket in CocoaHTTPserver was 7 years old. Update to version 7.6.4, which is 3 months old.

[qmfrederik]

A better way to do this is probably to use Carthage. I tried adding CocoaAsyncSockets as a Carthage dependency, but Xcode complained because CocoaAsyncSockets.h includes an @import Foundation statement. Appears to be related to this:

Xcode 11.4 turns the -Watimport-in-framework-header warning on by default. Using @import in framework headers is discouraged, because doing so requires all importers to use modules. (59222634) (FB7566046)

[mykola-mokhnach]

I tried adding CocoaAsyncSockets as a Carthage dependency, but Xcode complained because CocoaAsyncSockets.h includes an @import Foundation statement.

I think it is fine to disable warnings for such kind of issues in project opts

[mykola-mokhnach]

and add the lib to carthage