INSTALL.md: Add a few notes for Windows builds.

Signed-off-by: Ben Pfaff <[email protected]>
Acked-by: Gurucharan Shetty <[email protected]>

INSTALL.md

@@ -10,6 +10,7 @@ on a specific platform, please see one of these files:
   - [INSTALL.RHEL.md]
   - [INSTALL.XenServer.md]
   - [INSTALL.NetBSD.md]
+  - [INSTALL.Windows.md]
   - [INSTALL.DPDK.md]
 
 Build Requirements
@@ -28,6 +29,9 @@ you will need the following software:
         analysis and thread-safety checks.  For Ubuntu, there are
         nightly built packages available on clang's website.
 
+      * MSVC 2013.  See [INSTALL.Windows] for additional Windows build
+        instructions.
+
     While OVS may be compatible with other compilers, optimal
     support for atomic operations may be missing, making OVS very
     slow (see lib/ovs-atomic.h).