Update a call to PARSE_BOARD to Makefile-style in chipKIT file.
Fix path to avrdude for chipKIT's MPIDE installation.
Don't require an IDE preferences file, fallback to default sketchbook.

It should be possible to use the Makefile without ever running the
Arduino or chipKIT IDE. This change only looks for the preferences file
if the sketchbook path is not defined, and even then, will use the
default skethbook path if the preferences file is unavailable.
Merge pull request #104 from openxc/update-chipkit-parseboards

Update a call to PARSE_BOARD to Makefile-style in chipKIT file.
Merge pull request #108 from openxc/no-preferences-required

Don't require an IDE preferences file, fallback to default sketchbook.
Merge pull request #107 from openxc/chipkit-avrdude

Fix path to avrdude for chipKIT's MPIDE installation.
Rename ARDUINO_PORT to MONITOR_PORT to reflect support for other platforms.

This commit includes backwards compatibility with the ARDUINO_PORT flag if
that's set.

Fix #109
Merge branch 'serial-port-variable-name' of git://github.com/openxc/Arduino-Makefile into openxc-serial-port-variable-name