[client] spice: added new input:autoCapture mode

This new mode if enabled (disabled by default) will cause the client to
attempt to hold onto the mouse when a title/game has it captured in the
guest. This is best effort and is not a replacement for full capture
mode.

client/src/main.h

@@ -138,6 +138,7 @@ struct AppParams
   bool         mouseRedraw;
   int          mouseSens;
   bool         rawMouse;
+  bool         autoCapture;
 };
 
 struct CBRequest
@@ -215,6 +216,9 @@ struct CursorState
   /* the local X & Y position */
   struct DoublePoint pos;
 
+  /* the delta since last warp when in auto capture mode */
+  struct DoublePoint delta;
+
   /* the scale factor for the mouse sensitiviy */
   int sens;