EXT-3394 EXT-3297: Putting back the prefs volume slider.

Further discussions between Q and Joe resulted in the decision to keep
the master gain control in the sound prefs panel. Reverting to Lis'
original change, which should match exactly the state in viewer-2-0.

indra/newview/skins/default/xui/en/panel_preferences_sound.xml

@@ -400,13 +400,86 @@
      name="voice_input_device"
      top_pad="-2"
      width="200" />
+   <text
+     type="string"
+     length="1"
+     follows="left|top"
+     height="16"
+     layout="topleft"
+     left="165"
+     name="My volume label"
+     top_pad="5"
+     width="200">
+        My volume:
+    </text>
+      <slider_bar
+        control_name="AudioLevelMic"
+     follows="left|top"
+     height="17"
+     increment="0.05"
+     initial_value="1.0"
+     layout="topleft"
+     left="160"
+     max_val="2"
+     name="mic_volume_slider"
+     tool_tip="Change the volume using this slider"
+     top_pad="-2"
+     width="220" />
+    <text
+     type="string"
+     text_color="EmphasisColor"
+     length="1"
+     follows="left|top"
+     height="18"
+     layout="topleft"
+     left_pad="5"
+     name="wait_text"
+     top_delta="0"
+     width="110">
+        Please wait
+    </text>
+    <locate
+     height="20"
+     layout="topleft"
+     left_delta="0"
+     name="bar0"
+     top_delta="0"
+     width="20" />
+    <locate
+     height="20"
+     layout="topleft"
+     left_pad="2"
+     name="bar1"
+     top_delta="0"
+     width="20" />
+    <locate
+     height="20"
+     layout="topleft"
+     left_pad="2"
+     name="bar2"
+     top_delta="0"
+     width="20" />
+    <locate
+     height="20"
+     layout="topleft"
+     left_pad="2"
+     name="bar3"
+     top_delta="0"
+     width="20" />
+    <locate
+     height="20"
+     layout="topleft"
+     left_pad="2"
+     name="bar4"
+     top_delta="0"
+     width="20" />
           <icon
              height="18"
              image_name="Parcel_Voice_Light"
              left="80"
              name="speaker_icon"
              mouse_opaque="false"
-             top_pad="10"
+             top_pad="-8"
              visible="true"
              width="22" />
     <text