Open the serial port with O_NONBLOCK, and save and restore the port
state before exiting.
patch #5008: Patch for (5.1) ser_posix.c for O_NONBLOCK open and
restoring serial port state on close
Closes bug #12622: avrdude hangs on macosx/darwin with PL-2303
usb-to-serial and Butterfly
git-svn-id: svn://svn.savannah.nongnu.org/avrdude/trunk@627 81a1dc3b-b13d-400b-aceb-764788c761c2