* Don't overwrite the CMAKE_MODULE_PATH
* Allow linking libsodium statically with MSVC
* Allow finding libsodium the normal way on MSVC
* Allow using pthreads4w for pthreads on MSVC
* Fall back to find_package if pkg_find_module fails
* Don't pass incompatible compile flags to MSVC
* Also try to find Opus and libvpx using their canonical names
* Support building using conan
* Allow pkg_use_module to take a list of libraries to look for
* Build for Windows on Appveyor using conan
Also, added some #defines to make symbols visible that are in BSD but not
in UNIX. Solaris needs these, since it's fairly strict with its symbol
visibility in system headers.
Instead of hard-erroring when we don't find dependencies, we just don't
build the things requested and print a warning. This is less annoying to
users because we enable a bunch of things by default. This way, we can at
least build something with the default "cmake" invocation.
Tests are not actually ran on appveyor for now, since they all fault for
some reason. For now, we just build them. Also, some tests are disabled
on msvc entirely, because they don't even compile. We'll need to look
into those, later. They are disabled using `MSVC_DONT_BUILD`.
