* configure.in: Look for the x64 assembler ml64.exe when building 64-bit
  binaries, not ml.exe. Use the 64-bit tools in VC/bin/amd64, not
  the 32-bit cross-compiling tools in VC/bin/x86_amd64. We can
  currently build 64-bit only on a 64-bit OS anyway, for instance
  because of the unit tests.

* set_soenv.in: Set CPUNAME, CPU and OUTPATH appropriately for
  64-bit build. We end up with "wntsmcx12" for 64-bit MSVC 2008
  build. Drop sections for no longer supported MSVC versions. Don't
  talk about ".NET 2005" etc, ".NET" was part of the MS suite product
  name only in the 2003 version. Add Emacs and vim mode lines.