Changes:
* Move network interface configuration logic from bin/pattyd.c to
bin/if.c; implement a more robust state machine
* Move KISS TNC configuration code from bin/pattyd.c to bin/kiss.c
* Ensure configuration file name, line number, and erroneous part
of an expression are clearly indicated upon failure
Other changes:
* Improve bin/Makefile to rebuild objects when accompanying header
files change
* Refer to HEADERS_SUBDIR, not HEADER_SUBDIR, in Makefiles
188d43f98d