Handle the case of disk driver, supporting strat1 only

[Valery V. Sedletski]

It appears that fat32.ifs requires the disk driver with strat2 support, and it uses it in the cache code to queue the i/o requests. But it assumes that strat2 is supported, and we'll get a trap in FS_MOUNT in case it isn't. The drivers supporting strat1 only, do exist, for example, it is hd4disk.add driver for PAE ramdisk. It uses it because strat1 is simpler, and faster. Actually, hpfs.ifs works almost 10 times faster with strat1 switch given to hd4disk.add.

So, we need to handle gracefully the case of the disk driver, supporting strat1 only. -- We can just refuse to mount if the disk driver is strat1 only. This should be easy, but the full support for using strat1 only is harder to implement (need to change the cache logic)

[Valery V. Sedletski]

With trunk code, we now use FSH_DOVOLIO instead of directly calling the strat2 entry point. Also, FS_MOUNT now checks the presence of strat2, so, we now can safely use strat1 only disk driver. And, I tested successfully hd4disk.add with "/1" switch, and now see fat32 working with it. So, we can close this ticket.