HACK xaverius: Phase A C7 fix — resource types before registration, init symbol declared

- Call xaverius_device_init() before XaveriusRegistryInit() so DIX
  resource types exist before AddResource (C7)
- Call xaverius_device_fini() in xaverius_extension_fini() for symmetry
- Declare XaveriusExtensionInit() in xaverius.h (symbol consistency)
- Build clean (-Dwerror, no warnings)

Xext/xaverius/xaverius.c

@@ -50,4 +50,5 @@ void
 xaverius_extension_fini(void)
 {
     XaveriusRegistryFini();
+    xaverius_device_fini();
 }

Xext/xaverius/xaverius.h

@@ -280,6 +280,8 @@ typedef struct _XaveriusMemoryRec {
 void xaverius_extension_init(void);
 void xaverius_extension_fini(void);
 
+void XaveriusExtensionInit(void);
+
 int ProcXAveriusDispatch(ClientPtr client);
 int SProcXAveriusDispatch(ClientPtr client);