Allow and require passing files on command line of pgperltidy

pgperltidy as well as pgperlcritic and pgperlsyncheck now allow
passing files and directories on the command line, like pgindent does.
(Previously, they would always operate on the whole tree.)

Also, for consistency with pgindent's new behavior (as of b16259b3c1),
passing an argument is now required.  To get the previous default
behavior, use "pgperltidy ." for example.

Discussion: https://www.postgresql.org/message-id/flat/45aacd8a-5265-d9da-8df2-b8e2c0cf6a07%40eisentraut.org

src/tools/perlcheck/pgperlsyncheck

@@ -13,4 +13,4 @@ set -e
 # for zsh
 setopt shwordsplit 2>/dev/null || true
 
-find_perl_files | xargs -L 1 perl $INCLUDES -cw 2>&1 | grep -v OK
+find_perl_files "$@" | xargs -L 1 perl $INCLUDES -cw 2>&1 | grep -v OK