Despite of a few cosmetic things like adding ``irritating silly
parentheses'' around all return values, this mainly improves FDC reset
handling by no longer gratuitously resetting the FDC all the time
(which causes it to lose the notion of the current track) but only in
case of errors, and it sanitizes the block and offset calculations in
fdstrategy() and fdstate(). Some additional cleanup added by me, in
particular the large switch in fdstate() now always uses return to
break out, and no branch falls off the end of the switch statement
anymore. Per Bruce's suggestion, removed M_NOWAIT from the malloc()s
to simplify things.
Submitted by: bde (mostly)
fb35bd37f2