Invert Process_compare resolution so that superclass matches run first

* This removes duplicated code that adjusts the sort direction from every
  OS-specific folder.
* Most fields in a regular htop screen are OS-independent, so trying
  Process_compare first and only falling back to the OS-specific
  compareByKey function if it's an OS-specific field makes sense.
* This will allow us to override the sortKey in a global way without having
  to edit each OS-specific file.

dragonflybsd/DragonFlyBSDProcess.h

@@ -39,7 +39,7 @@ void Process_delete(Object* cast);
 
 void DragonFlyBSDProcess_writeField(const Process* this, RichString* str, ProcessField field);
 
-long DragonFlyBSDProcess_compare(const void* v1, const void* v2);
+long DragonFlyBSDProcess_compareByKey(const Process* v1, const Process* v2, ProcessField key);
 
 bool Process_isThread(const Process* this);