[io grant] Straighten out &lines/&words

- Just pass all args via captures; don't do own processing
- Make &words default to $*ARGFILES, just like the rest of the routines
    in this group.
- Add rudimentary IO::ArgFiles.words impl; will be replaced by IO::CatHandle

src/core/IO/ArgFiles.pm

@@ -147,6 +147,26 @@ my class IO::ArgFiles is IO::Handle {
         [~] @chunks;
     }
 
+    method words(IO::ArgFiles:D: |c) {
+        $!has-args = ?$!args unless $!has-args.defined;
+
+        return $*IN.words(|c) unless $!has-args;
+
+        my @chunks;
+        if $!io.defined && $!io.opened {
+            @chunks.append: $!io.words(:close, |c);
+        }
+
+        while $!args {
+            @chunks.append: words $!args.shift, |c;
+        }
+
+        # TODO Should this be a failure?
+        return Nil unless @chunks;
+
+        @chunks.Seq;
+    }
+
     method nl-in is rw {
         Proxy.new(
           FETCH => {

src/core/io_operators.pm

@@ -96,18 +96,10 @@ proto sub open(|) { * }
 multi sub open(IO() $path, |c) { IO::Handle.new(:$path).open(|c) }
 
 proto sub lines(|) { * }
-multi sub lines($what = $*ARGFILES, $limit = Inf, *%named) {
-    nqp::istype($limit,Whatever) || $limit == Inf
-      ?? $what.lines(|%named)
-      !! $what.lines($limit, |%named);
-}
+multi sub lines($what = $*ARGFILES, |c) { $what.lines(|c) }
 
 proto sub words(|) { * }
-multi sub words($what, $limit = Inf, *%named) {
-    nqp::istype($limit,Whatever) || $limit == Inf
-      ?? $what.words(|%named)
-      !! $what.words($limit, |%named);
-}
+multi sub words($what = $*ARGFILES, |c) { $what.words(|c) }
 
 proto sub get  (|) { * }
 multi sub get  (IO::Handle $fh = $*ARGFILES) { $fh.get  }