Add implicitGrab field to GrabInfoRec.

Is set when passive grab is implicit as result of a ButtonPress event. If this
is the case, we need to store the XI mask as well as the core mask to ensure
delivery of XI events during the grab's lifetime.

Remove all core grabs on other devices when client issues a GrabPointer or
GrabKeyboard request. Let's assume that the client really only wants one
device to interact, so this seems like a reasonable solution.

include/inputstr.h

@@ -333,9 +333,11 @@ typedef struct {
 #define FROZEN_NO_EVENT		5
 #define FROZEN_WITH_EVENT	6
 #define THAW_OTHERS		7
+
 typedef struct _GrabInfoRec {
-    TimeStamp	    grabTime;
-    Bool            fromPassiveGrab;
+    TimeStamp	    grabTime;           
+    Bool            fromPassiveGrab;    /* true if from passive grab */
+    Bool            implicitGrab;       /* implicit from ButtonPress */
     GrabRec         activeGrab;
     GrabPtr         grab;
     CARD8           activatingKey;