msvcrt: Fix errno set on dup from read-only file.

dlls/msvcrt/file.c

@@ -1244,6 +1244,7 @@ int CDECL _dup2(int od, int nd)
 
   if (info_nd == &MSVCRT___badioinfo)
   {
+      *_errno() = EBADF;
       ret = -1;
   }
   else if (info_od->wxflag & WX_OPEN)

dlls/msvcrt/tests/file.c

@@ -267,6 +267,12 @@ static void test_readmode( BOOL ascii_mode )
 
     close (fd);
     
+    fd = open ("fdopen.tst", O_RDONLY, _S_IREAD |_S_IWRITE);
+    errno = 0xdeadbeef;
+    ok(dup2(fd, -1) == -1, "dup2(fd, -1) succeeded\n");
+    ok(errno == EBADF, "errno = %d\n", errno);
+    close (fd);
+
     if (ascii_mode) {
         /* Open file in ascii mode */
         fd = open ("fdopen.tst", O_RDONLY);