On Windows do not take WINAPI HANDLE of non-socket connections

MariaDB and MySQL client libraries on Windows return zero value in
my_socket type when connection to server is not of socket type.

Zero value may be interpreted as file descriptor for stdin, so skip
processing of the zero value in socket related functions.

Author: pali

dbdimp.c

@@ -1401,6 +1401,10 @@ static int mariadb_dr_socket_cloexec(my_socket sock_os)
   DWORD flags;
   int error;
 
+  /* Ignore connections without valid socket handle */
+  if (sock_os == 0)
+    return 0;
+
   if (!GetHandleInformation(handle, &flags))
   {
     error = GetLastError();
@@ -2413,17 +2417,19 @@ static bool mariadb_dr_connect(
       /*
         Client library returns socket in my_socket type, which is C file
         descriptor on Linux or Windows native socket type on Windows.
+        On Windows it can be zero in case connection type is not socket.
         Perl requires sockets to always be in C file descriptor type,
         so on Windows associate it with C file descriptor via Perl's
         win32_open_osfhandle() function.
       */
 #ifdef _WIN32
-      imp_dbh->sock_fd = win32_open_osfhandle(sock_os, O_RDWR|O_BINARY);
+      imp_dbh->sock_fd = sock_os != 0 ? win32_open_osfhandle(sock_os, O_RDWR|O_BINARY) : -1;
 #else
       imp_dbh->sock_fd = sock_os;
 #endif
 
 #ifdef _WIN32
+      if (imp_dbh->sock_fd >= 0)
       {
         /*
          * Winsock SO_UPDATE_CONNECT_CONTEXT option needs to be set on the socket,