MDEV-28746 Wrong error code ER_BAD_DB_ERROR for long filenames

Add check for path length if CreateFile fails with ERROR_PATH_NOT_FOUND.

mysql-test/main/create_windows.result

@@ -0,0 +1,2 @@
+create table `...................................................`(i int);
+ERROR HY000: Can't create table `test`.`...................................................` (errno: 38 "Filename too long")

mysql-test/main/create_windows.test

@@ -0,0 +1,10 @@
+--source include/windows.inc
+
+# MDEV-28746 Wrong error code ER_BAD_DB_ERROR for long filenames
+
+# There are 51 dots in the table name below, with every dot encoded with 5
+# bytes in "mysql file name encoding", making the filename length 255 byte.
+# Adding drive and extension makes it exceed MAX_PATH= 260 bytes
+let $t = `SELECT(REPEAT('.',51))`;
+--error ER_CANT_CREATE_TABLE
+eval create table `$t`(i int);

mysys/my_winfile.c

@@ -250,13 +250,12 @@ File my_win_sopen(const char *path, int oflag, int shflag, int pmode)
   if ((osfh= CreateFile(path, fileaccess, fileshare, &SecurityAttributes, 
     filecreate, fileattrib, NULL)) == INVALID_HANDLE_VALUE)
   {
-    /*
-       OS call to open/create file failed! map the error, release
-       the lock, and return -1. note that it's not necessary to
-       call _free_osfhnd (it hasn't been used yet).
-    */
-    my_osmaperr(GetLastError());     /* map error */
-    DBUG_RETURN(-1);                 /* return error to caller */
+    DWORD last_error= GetLastError();
+    if (last_error == ERROR_PATH_NOT_FOUND && strlen(path) >= MAX_PATH)
+      errno= ENAMETOOLONG;
+    else
+      my_osmaperr(last_error);     /* map error */
+    DBUG_RETURN(-1);
   }
 
   if ((fh= my_open_osfhandle(osfh,