This change is the logical counterpart of SimGear's change from commit
79f869a7f32910197be72b21f6489fbbba02c836 that moved the following files
from simgear/misc to simgear/io/iostreams:
gzcontainerfile.cxx
gzcontainerfile.hxx
gzfstream.cxx (formerly zfstream.cxx)
gzfstream.hxx (formerly zfstream.hxx)
sgstream.cxx
sgstream.hxx
sgstream_test.cxx
* experimental clean-up / reduction on two of the FG headers:
(I'm going to await feedback on the developers list before doing more of
these, to avoiding going over files multiple times, but in principle it
seems pretty straightforward.)
* final fixes for SG_USING_STD removal
passing it along to FlightGear.) I notice that the serial port read only
seems to work correctly if I read one character at a time. Multicharacter
reads seem very unreliable.