64-bit Windows on AMD64/Intel EM64T is somewhat supported in the 7.0
and later release.  A collector can be built with Microsoft Visual C++ 2005.
The resulting test programs have been known to work at least once.
More testing would clearly be helpful.

NT_X64_STATIC_THREADS_MAKEFILE has been used in
this environment.  Copy this file to MAKEFILE, and then type "nmake"
in a Visual C++ command line window to build the static library
and the usual test programs.  To verify that the colllector is
at least somewhat functional, run gctest.exe.  This should create
gctest.exe.log after a few seconds.

This process is completely analogous to NT_STATIC_THREADS_MAKEFILE
for the 32-bit version.

A similar procedure using NT_X64_THREADS_MAKEFILE should be usable to
build the dynamic library.  Test_cpp.exe did not seem to run correctly this
way.  It seems that we're getting the wrong instances of operator new/delete
in some cases.  The C tests seemed OK.

Note that currently a few warnings are still generated by default,
and a number of others have been explicitly turned off in the makefile.