Fixing warnings under GCC4 in preparation to enable -Werror there as well:

* Replaced the use of offsetof() for structs that aren't PODs. Add a
  offset_of_member() macro to util/khash.h because that's what it's used for
  in our cases.
* Change the signature of add_debugger_command()/remove_debugger_command() on
  GCC > 2 to avoid the depricated conversion from string constants to char *.
* Adding some "suggested" parenthesis. I know that not everyone likes that, but
  it pointed out at least one bug that is fixed here as well.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@29113 a95241bf-73f2-0310-859d-f6bbb57e9c96

headers/private/kernel/util/khash.h

@@ -11,6 +11,12 @@
 
 #include <SupportDefs.h>
 
+// The use of offsetof() on non-PODs is invalid. Since many structs use
+// templated members (i.e. DoublyLinkedList) which makes them non-PODs we
+// can't use offsetof() anymore. This macro does the same, but requires an
+// instance of the object in question.
+#define offset_of_member(OBJECT, MEMBER) \
+	((size_t)((char*)&OBJECT.MEMBER - (char*)&OBJECT))
 
 // can be allocated on the stack
 typedef struct hash_iterator {