[PATCH 1/7] gdiplus: Make GpBitmap->bitmapbits access thread safe

[Vincent Povirk]

Copying the lock value in move_bitmap seems wrong to me, as it breaks
any locks on the destination. Locking the source doesn't make sense
because the caller is supposed to control the only reference to it.

I'm not sure it makes sense in free_image_data either, as it leaves
the image in an invalid state. Anything calling it should have a lock
if this is important.

I think it is possible to get unlock != true, when GdipImageRotateFlip
calls GdipBitmapLockBits.