WIP: floater_snapshot_feed.xml and code.

This is just a skeleton, roughly copied from the Postcoard
code, which is very similar. Nothing in indra/newview/llfloaterfeed.cpp
has been changed yet, apart from a few deletions (to make it compile)
and the literal replacement of "Postcard" with "Feed".
indra/newview/llfloatersnapshot.cpp was updated however to
open the new floater when one tries to upload a snapshot to the feed.
It is still needed to make a callback to saveFeed(), or rather to
move that function to the saveFeed that is in llfloatersnapshot.cpp.

indra/newview/skins/default/xui/en-us/floater_snapshot_feed.xml

@@ -0,0 +1,60 @@
+<?xml version="1.0" encoding="utf-8" standalone="yes" ?>
+<floater
+ can_minimize="false"
+ title="Post to My Profile Feed"
+ height="380"
+ width="480"
+ layout="topleft"
+ name="floater_snapshot_profile"
+ rect_control="FloaterSnapshotFeedRect">
+    <text
+     length="1"
+	 follows="top|left"
+     top="-180"
+     font="SansSerif"
+     height="16"
+     layout="topleft"
+     left="10"
+     name="caption_label"
+     right="-10"
+     type="string">
+     Enter text to post below:
+    </text>
+    <text_editor
+     follows="all"
+     height="155"
+     layout="topleft"
+     length="1"
+     max_length="700"
+     name="caption"
+     right="-10"
+	 bottom_delta="30"
+     type="string"
+     word_wrap="true"/>
+    <check_box
+     follows="left|bottom"
+     initial_value="true"
+     label="Include location"
+     layout="topleft"
+     left_delta="0"
+     name="add_location_cb"
+     bottom_delta="-25" />
+    <button
+     follows="right|bottom"
+     height="23"
+     label="Cancel"
+     layout="topleft"
+     name="cancel_btn"
+     right="-10"
+     bottom="10"
+     width="100"/>
+    <button
+     follows="right|bottom"
+     height="23"
+     label="Post"
+     layout="topleft"
+     left_delta="-106"
+     name="post_btn"
+     bottom_delta="0"
+     width="100"/>
+</floater>