[WIN32SS] Use the DCFLAGS and DCTYPE flags defined in ntgdi/dc.h instead of the old ones in include/ntgdihdl.h

The names of these new flags match the documented ones at
https://reactos.org/wiki/Techwiki:Win32k/DC
https://books.google.hr/books?id=-O92IIF1Bj4C&pg=PA197&lpg=PA197
and the gdikdx debug extension.

win32ss/gdi/ntgdi/dc.h

@@ -14,7 +14,7 @@ enum _FONT_STATE
 /* fl */
 #define DC_FL_PAL_BACK 1
 
-enum _DCFLAGS
+typedef enum _DCFLAGS
 {
     DC_DISPLAY           = 0x0001,
     DC_DIRECT            = 0x0002,
@@ -34,13 +34,13 @@ enum _DCFLAGS
 #if DBG
     DC_PREPARED          = 0x8000
 #endif
-};
+} DCFLAGS;
 
 typedef enum _DCTYPE
 {
-    DCTYPE_DIRECT = 0,
-    DCTYPE_MEMORY = 1,
-    DCTYPE_INFO = 2,
+    DCTYPE_DIRECT = 0,  /* Normal device context */
+    DCTYPE_MEMORY = 1,  /* Memory device context */
+    DCTYPE_INFO   = 2,  /* Information context   */
 } DCTYPE;