docs/about: Update the support statement for Windows

Our support statement for Windows currently talks about "Vista / Server
2008" - which is related to the API of Windows, and this is not easy
to understand for the non-technical users. Additionally, glib sets the
_WIN32_WINNT macro to 0x0601 already, which indicates the Windows 7 API,
so QEMU effectively depends on the Windows 7 API, too.

Thus let's bump the _WIN32_WINNT setting in QEMU to the same level as
glib uses and adjust our support statement in the documentation to
something similar that we're using for Linux and the *BSD systems
(i.e. only the two most recent versions), which should hopefully be
easier to understand for the users now.

And since we're nowadays also compile-testing QEMU with MSYS2 on Windows
itself, I think we could mention this build environment here, too.

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/880
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Stefan Weil <sw@weilnetz.de>
Message-Id: <20220513063958.1181443-1-thuth@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
diff --git a/configure b/configure
index 0cc8c87..103a7b0 100755
--- a/configure
+++ b/configure
@@ -1486,6 +1486,8 @@
 ##########################################
 # glib support probe
 
+# When bumping glib_req_ver, please check also whether we should increase
+# the _WIN32_WINNT setting in osdep.h according to the value from glib
 glib_req_ver=2.56
 glib_modules=gthread-2.0
 if test "$modules" = yes; then