Remove memory debugging/tracing support and all related options

Drop disabled by default and pretty useless memory tracing code and all
the overlapping and poorly documented build options related to it.

Remove memory.cpp entirely and update all the make/project files, but
preserve the now completely trivial wx/memory.h for compatibility and
also keep including wx/string.h from wx/object.h as it seems like a lot
of existing code actually depends on this, even if it should not.

Replace the options in the propgrid sample with a couple of other
debug-related options that were not used before to avoid leaving the
"Debugging Section" completely empty.

include/wx/defs.h

@@ -850,13 +850,6 @@ typedef short int WXTYPE;
 /*  compiler specific settings */
 /*  ---------------------------------------------------------------------------- */
 
-/*  where should i put this? we need to make sure of this as it breaks */
-/*  the <iostream> code. */
-#if defined(__WXDEBUG__)
-#    undef wxUSE_DEBUG_NEW_ALWAYS
-#    define wxUSE_DEBUG_NEW_ALWAYS 0
-#endif
-
 #include "wx/types.h"
 
 #ifdef __cplusplus