Add debugging helper for std::tuple and add
a corresponding dumper test for it.
With this in place, the std::tuple variable and its elements
in the "tuple.cpp" sample program from QTCREATORBUG-25865 are
shown as expected on both, Linux (libstdc++) with GDB or LLDB and with
an MSVC build with CDB on Windows.
A debugging helper for libc++ had already been added in commit
34ff9c97e6.
Task-number: QTCREATORBUG-25865
Change-Id: I24b3d36b5daa26fd4fcb073c4df79015dfe752fc
Reviewed-by: hjk <hjk@qt.io>
4aaf7f2689