MSVC.README.rst: Update VS 2008/x64 build notes

It appears that tests/repository/gitypelibtest.c needs to be added to
the list of files that we must change the optimization flag from /O2 to
/O1 in order that the Visual Studio 2008 x64 compiler does not hang, due
to compiler optimization issues.
5 jobs for <span class="ref-name">msvc-readme-stable</span> in 13 minutes and 17 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Build
passed #290101
fedora-x86_64-autotools

00:02:38

passed #290100
fedora-x86_64-meson

00:02:05

passed #290103
win32
msys2-mingw32-autotools

00:07:30

passed #290102
win32
msys2-mingw32-meson

00:03:08

passed #290104
win32
vs2017-x64-meson

00:04:45