Is __OPENTRANSPORTPROVIDERS__ (still) needed

...to be set before including Carbon/Carbon.h?  Was originally introduced with
c34f2e30 "INTEGRATION: CWS pj51: #i61959# patch
applied", but might just be cargo cult these days.

Change-Id: I20cdc938d28e075614f6711a06ab785700833aff
Reviewed-on: https://gerrit.libreoffice.org/24293Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

sal/osl/unx/system.hxx

@@ -197,7 +197,6 @@
 #endif
 
 #ifdef MACOSX
-#define __OPENTRANSPORTPROVIDERS__ // these are already defined
 #define TimeValue CFTimeValue      // Do not conflict with TimeValue in sal/inc/osl/time.h
 #include <Carbon/Carbon.h>
 #undef TimeValue