libssh2_channel_process_startup.3: clean up
libssh2_channel_process_startup.3: clean up

Remove the references to the macro-fied shortcuts as they have their own
individual man pages.

Made the prototype different and more readable.

libssh2/libssh2,libssh2/libssh2,libssh2/libssh2,libssh2/libssh2