[DynInst_API:] RFC: require users to have C++11

[Josh Stone <jistone@xxxxxxxxxx>]

Dyninst already requires C++11 features to build itself, but maintains
support for pre-C++11 in the public interface.  This means for instance
that we have to use std::tr1::unordered_map and boost::shared_ptr
instead of the C++11 std::unordered_map and std::shared_ptr.

For a small example motivation, I was looking at the enormous function
SyscallInformation::SyscallInformation(), which has to fill the mapping
tables.  Right now it does this with individual insert() calls, which
generates a lot of code.  I'm thinking of a few ways to make this more
data-driven, and the easiest would be with C++11 initializer lists:

  Linux_Arch_ppc64_syscallNames.insert({
    {0, "restart_syscall"},
    {1, "exit"},
    {2, "fork"},
    /* ... */
  });

Now, this map is purely internal, so we could just go ahead convert it
from the generic dyn_hash_map to a C++11 std::unordered_map and go
crazy.  But I'd like to have the opportunity to use C++11 throughout the
code, without worrying about what's in public headers.

Assuming we want to maintain RHEL6 support (GCC 4.4), that still limits
us to some earlier "C++0x" features, listed at the link below.  I'm not
sure about the state of Dyninst's minimum MSVC on the Windows side.
https://gcc.gnu.org/gcc-4.4/cxx0x_status.html

FWIW, GCC6 leaped up to -std=gnu++14 as the default mode.  This is in
Fedora 24 now and will be in Ubuntu 16.10.


Could we make this change in master now for Dyninst 9.3?  Wait for 10.0?