Merge branch 'pr/423'

Revert "no engine specifier"

This reverts commit 7c96183.

fix include for 5.3

Merge branch 'pr/387' into feature-5.3

5.2 update and extra auth

can append more key:value pairs to auth map sent on connect

5.2 update and extra auth

can append more key:value pairs to auth map sent on connect

Actually fix binary messages

- Binary partials have no frame messages anymore
- Tested on a png echo emit loop at 120fps
- Catch attempt to decode a binary field with a null json value (e.g. property mismatch)

Update SocketIOClient.uplugin

Update SocketIOClient.uplugin

- bumped for #374

change libopus include

- 5.1 engine seems to prefer opus 1.1