io: Improve wrapper-stream dispatch performance

Methods on subclasses of <wrapper-stream> often make heavy use of
inner-stream, which is an open generic function. To ensure that calls
to inner-stream are dispatched efficiently, this change adds sealing
definitions for inner-stream on <wrapper-stream> subclasses.

* sources/io/streams/wrapper-stream.dylan
  (inner-stream on <wrapper-stream>): Make method inline due to its
   simplicity and performance benefit.

* sources/io/streams/indenting-streams.dylan:
  Seal inner-stream on <indenting-stream>.

* sources/lib/coloring-stream/coloring-stream.dylan:
  Seal inner-stream on <coloring-stream>.

* sources/lib/progress-stream/progress-stream.dylan:
  Seal inner-stream on <progress-stream>.

* sources/lib/llvm/bitcode.dylan: Seal inner-stream on
  <bitcode-stream>.

sources/io/streams/indenting-streams.dylan

@@ -54,6 +54,7 @@ end;
 
 define sealed domain make(singleton(<indenting-stream>));
 define sealed domain initialize(<indenting-stream>);
+define sealed domain inner-stream(<indenting-stream>);
 
 define constant $spaces :: <byte-string>
   = "                                                                "; // 64

sources/io/streams/wrapper-stream.dylan

@@ -31,7 +31,7 @@ define sealed domain unlock-stream (<simple-wrapper-stream>);
 define open generic inner-stream
     (wrapper-stream :: <wrapper-stream>) => (stream :: <stream>);
 
-define method inner-stream
+define inline method inner-stream
     (wrapper-stream :: <wrapper-stream>) => (stream :: <stream>)
   wrapper-stream.%inner-stream;
 end method inner-stream;

sources/lib/coloring-stream/coloring-stream.dylan

@@ -10,6 +10,7 @@ end class <coloring-stream>;
 
 define sealed domain make(singleton(<coloring-stream>));
 define sealed domain initialize(<coloring-stream>);
+define sealed domain inner-stream(<coloring-stream>);
 
 define sealed method make
     (class == <coloring-stream>, #rest initargs,

sources/lib/llvm/bitcode.dylan

@@ -24,6 +24,8 @@ define class <bitcode-stream> (<wrapper-stream>)
   slot bitcode-records :: <object-table> = make(<object-table>);
 end class;
 
+define sealed domain inner-stream (<bitcode-stream>);
+
 define method bitcode-flush
     (stream :: <bitcode-stream>)
  => ();

sources/lib/progress-stream/progress-stream.dylan

@@ -24,6 +24,8 @@ define sealed method make
   end if
 end method;
 
+define sealed domain inner-stream (<progress-stream>);
+
 define class <dummy-progress-stream> (<progress-stream>)
 end class;