Fix guarding macro in include/internal/sockets.h

The guard was checked but never defined.  Also, rename it to reflect
that this is an internal header file, not a public one.
Reviewed-by: NRich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/4254)

include/internal/sockets.h

@@ -8,7 +8,8 @@
  */
 
 
-#ifndef HEADER_OPENSSL_SOCKETS
+#ifndef HEADER_INTERNAL_SOCKETS
+# define HEADER_INTERNAL_SOCKETS
 
 # if defined(OPENSSL_SYS_VXWORKS) || defined(OPENSSL_SYS_UEFI)
 #  define NO_SYS_PARAM_H
@@ -125,38 +126,37 @@ struct servent *PASCAL getservbyname(const char *, const char *);
 #  endif
 # endif
 
-#endif
-
-#define get_last_socket_error() errno
-#define clear_socket_error()    errno=0
+# define get_last_socket_error() errno
+# define clear_socket_error()    errno=0
 
-#if defined(OPENSSL_SYS_WINDOWS)
+# if defined(OPENSSL_SYS_WINDOWS)
 #  undef get_last_socket_error
 #  undef clear_socket_error
 #  define get_last_socket_error() WSAGetLastError()
 #  define clear_socket_error()    WSASetLastError(0)
 #  define readsocket(s,b,n)       recv((s),(b),(n),0)
 #  define writesocket(s,b,n)      send((s),(b),(n),0)
-#elif defined(__DJGPP__)
+# elif defined(__DJGPP__)
 #  define WATT32
 #  define WATT32_NO_OLDIES
 #  define closesocket(s)          close_s(s)
 #  define readsocket(s,b,n)       read_s(s,b,n)
 #  define writesocket(s,b,n)      send(s,b,n,0)
-#elif defined(OPENSSL_SYS_VMS)
+# elif defined(OPENSSL_SYS_VMS)
 #  define ioctlsocket(a,b,c)      ioctl(a,b,c)
 #  define closesocket(s)          close(s)
 #  define readsocket(s,b,n)       recv((s),(b),(n),0)
 #  define writesocket(s,b,n)      send((s),(b),(n),0)
-#elif defined(OPENSSL_SYS_VXWORKS)
+# elif defined(OPENSSL_SYS_VXWORKS)
 #  define ioctlsocket(a,b,c)          ioctl((a),(b),(int)(c))
 #  define closesocket(s)              close(s)
 #  define readsocket(s,b,n)           read((s),(b),(n))
 #  define writesocket(s,b,n)          write((s),(char *)(b),(n))
-#else
+# else
 #  define ioctlsocket(a,b,c)      ioctl(a,b,c)
 #  define closesocket(s)          close(s)
 #  define readsocket(s,b,n)       read((s),(b),(n))
 #  define writesocket(s,b,n)      write((s),(b),(n))
-#endif
+# endif
 
+#endif