pic inconsistently diagnoses carriage returns

[Doug McIlroy]

pic 1.21 is inconsistent about detecting carriage-return characters.
For example, if pic is given this file with CRLF line terminations
(as may happen when used in Windows), carriage returns are
diagnosed only on the last two lines.  Pic also reports "there is
no variable 'f'".  (The first .PS is not recognized because
it is delimited by \r.)

.PS
define f { $1 }
.PE
.PS 2i
a = f(0)
.PE

Things get really mysterious if the first .PS...PE is in a separate
file, with CRLF terminations, that is included via .PS <source
in a second file with LF terminations.  Then the only
diagnostic is "there is no variable 'f'".  (In fact this
scenario is what brought the problem to my attention.)