Include missing header to segfault seen on Xorg startup with nv driver,

savage driver seems to have same problem.

help and cluebatting from matthieu@ and guenther@

OK matthieu@

driver/xf86-video-nv/src/nv_driver.c

@@ -32,6 +32,7 @@
 
 #include "xf86int10.h"
 #include "vbeModes.h"
+#include "xf86Modes.h"
 
 const   OptionInfoRec * RivaAvailableOptions(int chipid, int busid);
 Bool    RivaGetScrnInfoRec(PciChipsets *chips, int chip);

driver/xf86-video-savage/src/savage_driver.c

@@ -54,6 +54,7 @@
 
 
 #include "xf86xv.h"
+#include "xf86Modes.h"
 
 #include "savage_driver.h"
 #include "savage_pciids.h"