main/libwebsockets: split package into multiple configurations

The websockets library supports several event loops, but sadly it links against them. This means we would always have to pull in those dependencies when installing a 'fat' libwebsockets.

To keep with the 'lean and mean' principle of Alpine Linux, we will over various variants of libwebsockets to satisfy all needs.

One risk that does follow from this, is that if packages have conflicting dependencies, but that is something to be solved upstream, either via plugins or multiple libraries that can be installed alongside.

Signed-off-by: Olliver Schinagl oliver@schinagl.nl

The upstream initial discussion is here: https://github.com/warmcat/libwebsockets/issues/2021 the chosen solution resembles that of Zabbix as discussed with @kdaudt on IRC.