2006/11/17 PSB
- Added SIGUSR1 trapping.  When received, schedules data file re-scan.
- Added pidfile configuration option
- PID is logged to pidfile, enabling "kill -USR1 `cat pidfile`"
- The " - " end/start separator is used only if the input line width
  is > the display width.  I.e., only if scrolling.
- Added refresh_file_name config option
- When the file specified by refresh_file_name is created, pertd will
  schedule a data file re-scan.
- Added PERTD_VERSION #define in pert_interf.h
- Created a constant for the LCD screen width and substituted that
  wherever the width was hardcoded.


7/16/2006
- Changed the way the data files are handled.
	1. The last modified timestamp is remembered and the data file is not
	re-read unless the file timestamp has changed.
	2. The 1024 char limit has been removed.  All data in the file is read and
	displayed.
	3. Multi-line data files are now handled.  If there is more than 1 line in
	the data file, the lines are concatinated seperated by spaces, to display on
	the LCD.
- Scrolling is smoother.  The seperator between the end/start of the data line
now scrolls smooth instead of just disappearing when the end of data line is
reached.
- The delay between screen refreshes is now configurable in pertd.conf.
- Removed the delay function from pertd_interf.c and replaced it with a
sleep_us for 1 ms.  A 1 ms delay between chars sent to the LCD works fine
while no delay will result in garbled output.  *** Note that this change
drastically lowered CPU usage.
