This TECO macro makes a TECO command string printable by converting
escape characters to dollar signs and all control characters to the
tilde-character string which is usually printed on the terminal, except
for ^I (tab), ^M (cr), ^L (ff), and ^J (lf).


<
z-."e1;'        ! if at end of buffer,  exit the loop !
0a-31"gcf<'     ! it it's already printable,  skip it !
0a-27"ei$df<'  ! if it's ESCAPE,  make it into a dollar-sign !
0a-13"ecf<'     ! if it's carriage return,  skip it !
0a-10"ecf<'     ! if it's line feed,  skip it !
0a-9"ecf<'      ! if it's TAB, skip it !
0a-12"ecf<'     ! if it's form feed,  skip it !
i^0a+64id
>