Simplify return & fshut() logic

Get rid of the !!()-constructs and use ret where available (or introduce it).

In some cases, there would be an "abort" on the first fshut-error, but we want
to close all files and report all warnings and then quit, not just the warning
for the first file.

col.c

@@ -190,6 +190,8 @@ usage(void)
 int
 main(int argc, char *argv[])
 {
+	int ret = 0;
+
 	ARGBEGIN {
 	case 'b':
 		backspace = 1;
@@ -217,5 +219,7 @@ main(int argc, char *argv[])
 	col();
 	flush();
 
-	return !!(fshut(stdin, "<stdin>") + fshut(stdout, "<stdout>"));
+	ret |= fshut(stdin, "<stdin>") | fshut(stdout, "<stdout>");
+
+	return ret;
 }