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.

include/data.h

@@ -99,6 +99,14 @@ typedef enum {
     B_MOUSE = 1
 } input_type_t;
 
+/**
+ * Mouse pointer warping modes.
+ */
+typedef enum {
+    POINTER_WARPING_OUTPUT = 0,
+    POINTER_WARPING_NONE = 1
+} warping_t;
+
 /**
  * Stores a rectangle, for example the size of a window, the child window etc.
  * It needs to be packed so that the compiler will not add any padding bytes.