dtwm: Cleanup some implicit definitions

Mostly this is adding appropriate #includes and declarations,
but for WmImage.c we also change from using the proper name
for XmeGetMask, rather than the identical but renamed
version _DtGetMask which is not exported in any header.

cde/programs/dtwm/WmResParse.h

@@ -48,9 +48,9 @@ extern Boolean         FindDtSessionMatch(int commandArgc,
 					   WmScreenData *pSD, 
 					   char **pWorkSpaceList,
 					   char *clientMachine);
-extern void            WmDtGetHelprgs(char *args, 
-				       unsigned char** volume, 
-				       unsigned char** topic, 
+extern void            WmDtGetHelpArgs(char *args, 
+				       unsigned char* volume, 
+				       unsigned char* topic, 
 				       int *argsCount);
 extern void GetActionIndex (int tableSize, int *actionIndex);
 extern void            GetFunctionTableValues (int *execIndex, int *nopIndex,