Eliminate refcount.h workaround for uStreamer compilation

[mtlynch]

I'm not sure if this is a Janus bug or a uStreamer bug, but the uStreamer Janus plugin won't compile unless we manually fix a C #include line in a Janus header.

It looks like Janus expects clients to have the janus header directory directly included when a plugin compiles, whereas uStreamer expects to only have the include/ dir included and expects Janus headers to be under <janus/whatever.h>, which seems reasonable.