Disable C++11 support for ICC on OS X

ICC does support C++11, but the Apple headers contain invalid code that
Clang seems to accept. In C++11 mode, code using CF_ENUM expands to:

  typedef enum EnumName : CFIndex EnumName; enum EnumName {

Which is valid Objective C++, but not valid C++.

Bug reports to Intel and to Apple are pending.

Discussed-on: https://groups.google.com/a/isocpp.org/d/msg/std-discussion/yDfkDo6C0BM/EVWzwjVbyh4J
Change-Id: I7d501e94212a90f5c7197a3b56016dadac2c44ad
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>