+/* Open a file and see whether the initial lines match the "!% ..." format
+ used for ICL commands. Stop when we reach a line that doesn't.
+
+ This does not do line break conversion. It just reads to the next
+ \n (and ignores \r as whitespace). Therefore it will work on Unix and
+ DOS source files, but fail to cope with Mac-Classic (\r) source files.
+ I am not going to worry about this, because files from the Mac-Classic
+ era shouldn't have "!%" lines; that convention was invented well after
+ Mac switched over to \n format.
+ */