fsiec bugs

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• FSIEC does not recognize chdir paths when reading directories
  from the bus (i.e. C64 reads from IEEE488 bus and CSA drive is the
  fsibm drive), files are ok.

• when fsiec on C64 is parallel but doesn't find the interface, it
  dies too ungracefully...

• when path overflows, behaviour is undefined

• FSIEC hangs on disk full with C64 parallel IEC bus interface (and probably
  others too)

• FSIEC (on CS/A65) seems not to release the interface semaphore after
  init every time?

• serial IEC bus for CS/A65 architecture only works with 1MHz (is this a bug?)

• C64 fsiec filesystem (serial/parallel?) reads one byte from file even
  when it's not found (in VICE)

• fsiec, fsibm and fsdev ignore stream brk/push/pull flags, and don't set
  stream error flags (only fsiec sets SCE_[RW]ERRM flags).

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Multiple open files may result in hangs, like:
hexdump ls > ls.hex
or
ls ' hexdump > foo.txt

Note: may be related to #17

[fachat]

No, most likely not related to #17, as it also happens with
hexdump ls > d:ls.txt
with a 1571 as unit 8/c: and an XS1541 drive as unit 9/d: