Another round of const correctness fixes.

diff --git a/include/user.h b/include/user.h
index 7eef76c..ce2e689 100644
--- a/include/user.h
+++ b/include/user.h
@@ -40,8 +40,8 @@
 #define USER_HEAP_LIN_ADDR(handle)  \
          ((handle) ? MapSL(MAKESEGPTR(USER_HeapSel, LOWORD(handle))) : NULL)
 
-#define GET_WORD(ptr)  (*(WORD *)(ptr))
-#define GET_DWORD(ptr) (*(DWORD *)(ptr))
+#define GET_WORD(ptr)  (*(const WORD *)(ptr))
+#define GET_DWORD(ptr) (*(const DWORD *)(ptr))
 
 #define USUD_LOCALALLOC        0x0001
 #define USUD_LOCALFREE         0x0002