The top level socket directory is now called XRDP_SOCKET_ROOT_PATH.
Below that are user-specific directories referred to with the
XRDP_SOCKET_PATH macro - this name is hard-coded into xorgxrdp and
the audio modules as an environment variable.
XRDP_SOCKET_PATH now looks like $XRDP_SOCKET_ROOT_PATH/<uid>
XRDP_SOCKET_PATH is only writeable by the user, and readable by the user
and the xrdp process.
Use XRDP_SOCKET_PATH in file_loc.h
Don't define any non-socket paths in file_loc.h, they should come from
the makefiles.
Define all paths unconditionally, they should not be defined elsewhere.
Pass XRDP_SOCKET_PATH as environment variable to the backends.
