Add configuration option for disabling mouse warping

This patch adds a new configuration option "mouse_warping [output|none]".

When mouse warping is disabled, mouse cursor does not jump to middle of current
screen when changing workspaces between multiple outputs. This introduces a
"special" cursor state, where focus is in one window and cursor on another.
Useful for eg. scrolling a web page with mouse wheel while typing into another
window on keyboard.

parser-specs/config.spec

@@ -32,6 +32,7 @@ state INITIAL:
   'for_window'                             -> FOR_WINDOW
   'assign'                                 -> ASSIGN
   'focus_follows_mouse'                    -> FOCUS_FOLLOWS_MOUSE
+  'mouse_warping'                          -> MOUSE_WARPING
   'force_focus_wrapping'                   -> FORCE_FOCUS_WRAPPING
   'force_xinerama', 'force-xinerama'       -> FORCE_XINERAMA
   'workspace_auto_back_and_forth'          -> WORKSPACE_BACK_AND_FORTH
@@ -172,6 +173,11 @@ state FOCUS_FOLLOWS_MOUSE:
   value = word
       -> call cfg_focus_follows_mouse($value)
 
+# mouse_warping warping_t
+state MOUSE_WARPING:
+  value = 'none', 'output'
+      -> call cfg_mouse_warping($value)
+
 # force_focus_wrapping
 state FORCE_FOCUS_WRAPPING:
   value = word