Event lib support as it has been isn't scaling well, at the low level
libevent and libev headers have a namespace conflict so they can't
both be built into the same image, and at the distro level, binding
all the event libs to libwebsockets.so makes a bloaty situation for
packaging, lws will drag in all the event libs every time.
This patch implements the plan discussed here
https://github.com/warmcat/libwebsockets/issues/1980
and refactors the event lib support so they are built into isolated
plugins and bound at runtime according to what the application says
it wants to use. The event lib plugins can be packaged individually
so that only the needed sets of support are installed (perhaps none
of them if the user code is OK with the default poll() loop). And
dependent user code can mark the specific event loop plugin package
as required so pieces are added as needed.
The eventlib-foreign example is also refactored to build the selected
lib support isolated.
A readme is added detailing the changes and how to use them.
https://libwebsockets.org/git/libwebsockets/tree/READMEs/README.event-libs.md
This gives a valgrind result for lws-minimal-http-server-event-lib-foreign
that's clean for lws pieces, although glib is always dirty wrt thread local
storage and hashtable.
https://libwebsockets.org/pipermail/libwebsockets/2019-April/007937.html
thanks to Bruce Perens for noting it.
This doesn't change the intention or status of the CC0 files, they were
pure CC0 before (ie, public domain) and they are pure CC0 now. It just
gets rid of the (C) part at the top of the dedication which may be read
to be a bit contradictory since the purpose is to make it public domain.
1) update the logos to svg
2) add svg icon for strict security policy where used
3) define new vhost option flag to enforce sending CSP headers
with the result code
4) add vhost option flag to minimal examples to
enforce sending CSP where applicable
5) Go through all the affecting examples confirming they
still work
6) add LWS_RECOMMENDED_MIN_HEADER_SPACE constant (currently
2048) to clarify when we need a buffer to hold headers...
with CSP the headers have become potentially a lot
larger.
