text: Add reset requets to protocol

Add a reset request to the text_model interface and a reset event to the
input_method_context interface. Use it to reset the pre-edit buffers in
the example keyboard when the cursor is moved in the example editor
client.

Signed-off-by: Jan Arne Petersen <jpetersen@openismus.com>

protocol/input-method.xml

@@ -68,6 +68,8 @@
       <arg name="cursor" type="uint"/>
       <arg name="anchor" type="uint"/>
     </event>
+    <event name="reset">
+    </event>
   </interface>
 
   <interface name="input_method" version="1">

protocol/text.xml

@@ -67,6 +67,8 @@
       </description>
       <arg name="seat" type="object" interface="wl_seat"/>
     </request>
+    <request name="reset">
+    </request>
     <request name="set_micro_focus">
       <arg name="x" type="int"/>
       <arg name="y" type="int"/>