loader: issue edd probe before legacy ah=08 and detect no media

[tsoome]

Summary

while probing for drives, use int13 extended info before standard one and
provide workaround for case we are not getting needed information in case
of floppy drive.

In case of INT13 errors, there are (at least) 3 error codes appearing in case
of missin media - 20h, 31h and 80h. Flag the no media and do not print an
error.

[tsoome]

Test the presence of floppy device before attempting to read information
about it. We can get bogus information about non-existing floppy devices.

[imp]

stand/i386/libi386/biosdisk.c

820 ↗

(On Diff #49822)

Are these error codes documented somewhere?

[tsoome]

stand/i386/libi386/biosdisk.c

820 ↗

(On Diff #49822)

It is quite wild west there:

http://www.bioscentral.com/misc/biosint13.htm does list 20h and 80h, but in generic form.
http://home.teleport.com/~brainy/interrupts.htm does list 31h

[imp]

OK. Since there's not a simple place to point people, let's get this in.

stand/i386/libi386/biosdisk.c

820 ↗

(On Diff #49822)

fun!