Modify the windows amd64 unwinder to work as jitted code unwinder on Unix

Modify the windows amd64 unwinder to work as jitted code unwinder on Unix

Update the windows amd64 unwinder from its source to the latest version
and add context pointers updating that was excluded before.
Change methods of the OOPStackUnwinder and OOPStackUnwinderAMD64 to be
static, since the base class has no data members and the unwinding is
always using the processor specific subclass.
Modify the code so that it is built in two flavors. The first one
is the DAC flavor which is used by the debugger. The second one will be
used for jitted code stack frames unwinding on non-Windows systems.