iundecl.icn: Program to find undeclared Icon identifiers

This program invokes icont to find undeclared variables in an Icon
source program.  The output is in the form of a "local" declaration,
preceded by a comment line that identifies that procedure and file
name from whence it arose.  Beware that undeclared variables aren't
necessarily local, so any which are intended to be global must be
removed from the generated list.

Multiple files can be specified as arguments, and will be processed
in sequence.  A file name of "-" represents the standard input file.
If there are no arguments, standard input is processed.

The program works only if procedures are formatted such that the
keywords "procedure" and "end" are the first words on their
respective lines.

Only for UNIX, since the "p" (pipe) option of open() is used.