bpo-34217: Use lowercase header for Windows (GH-8453)

(cherry picked from commit 6cf82559)
Co-authored-by: erikjanss <erik.janssens@conceptive.be>

Modules/socketmodule.h

@@ -28,7 +28,7 @@
  * I use SIO_GET_MULTICAST_FILTER to detect a decent SDK.
  */
 # ifdef SIO_GET_MULTICAST_FILTER
-#  include <MSTcpIP.h> /* for SIO_RCVALL */
+#  include <mstcpip.h> /* for SIO_RCVALL */
 #  define HAVE_ADDRINFO
 #  define HAVE_SOCKADDR_STORAGE
 #  define HAVE_GETADDRINFO

PC/getpathp.c

@@ -89,7 +89,7 @@
 #endif
 
 #include <windows.h>
-#include <Shlwapi.h>
+#include <shlwapi.h>
 
 #ifdef HAVE_SYS_TYPES_H
 #include <sys/types.h>