added CS_DROPSHADOW, needed by latest version of wine's user32 test app

reactos/w32api/include

diff -u -r1.4 -r1.5
--- winuser.h	9 Apr 2004 20:03:21 -0000	1.4
+++ winuser.h	28 May 2004 03:43:12 -0000	1.5
@@ -593,6 +593,7 @@

 #define CS_SAVEBITS 2048
 #define CS_VREDRAW 1
 #define CS_IME 0x10000

+#define CS_DROPSHADOW 0x20000

 #define GCW_ATOM (-32)
 #define GCL_CBCLSEXTRA (-20)
 #define GCL_CBWNDEXTRA (-18)