Add SOL_VSOCK from Linux 6.7 to bits/socket.h

Linux 6.7 adds a constant SOL_VSOCK (recall that various constants in
include/linux/socket.h are in fact part of the kernel-userspace API
despite that not being a uapi header).  Add it to glibc's
bits/socket.h.

Tested for x86_64.

sysdeps/unix/sysv/linux/bits/socket.h

@@ -172,6 +172,7 @@ typedef __socklen_t socklen_t;
 #define SOL_MPTCP	284
 #define SOL_MCTP	285
 #define SOL_SMC		286
+#define SOL_VSOCK	287
 
 /* Maximum queue length specifiable by listen.  */
 #define SOMAXCONN	4096