remove hack for debian etch limits.h

The debian etch distro was end-of-life a long time ago so we no
longer need the ULLONG_MAX hack. In any case gnulib now provides
an equivalent fix by default, and so our definition now triggers
syntax-check rule failure

src/internal.h:#    define ULLONG_MAX   ULONG_LONG_MAX
maint.mk: define the above via some gnulib .h file
maint.mk:843: recipe for target 'sc_prohibit_always-defined_macros' failed
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

src/internal.h

@@ -114,11 +114,6 @@
 #    define __GNUC_PREREQ(maj, min) 0
 #   endif
 
-/* Work around broken limits.h on debian etch */
-#   if defined _GCC_LIMITS_H_ && ! defined ULLONG_MAX
-#    define ULLONG_MAX   ULONG_LONG_MAX
-#   endif
-
 #  endif /* __GNUC__ */
 
 /**