I have reversed merged the two commits that moved the function named
rtcpd_SignalFilePositioned out of the source file rtcpd_Tape.c and into its
own dedicated file.

I have taken this action because I will implement the buffered tape marks over
multiple files in a different way which does not require cutting rtcpd_Tape.c
into many separate files.  This change of direction has been made because the
functions defined in rtcpd_Tape.c share too many global variables and too many
locally defined macros and datatypes.