Add support for external pthreads lib on windows and some docs about how to do.
It can build with LWS_WITH_THREADPOOL and LWS_WITH_MINIMAL_EXAMPLES including the
pthreads-dependent ones without warnings or errors on windows platform as well with this.
pthreads_t can be anything, including a struct - not a pointer-to-a-struct
but the struct itself. These can't be cast to a void * for printing as they can
on linux, where the base type is a pointer.
Let's fix all the usage of those to determine their own thread index in terms
of the meaning to the program rather than as a tid.
Fix pthreads detection in the minimal examples and add it where needed.
Fix unistd.h include to be conditional on not WIN32
With this, -DLWS_WITH_MINIMAL_EXAMPLES=1 is happy and warning-free
on windows.
This adds an lws cmake option that builds all the minimal examples as part of lws,
it's useful for QA.
It adds a macro to examples that depend on a particular lws configuration to understand
they should just null out their project definition in builds where the lws configuration
requirement is not met, and we are building as part of lws.
It also adapts all the example library additions to select the just-built-but-not-yet-installed
library in the case it is built as part of lws. If built standalone, it now uses the cmake
platform-abstracted way to add the library requirement too.
