  1. Reduce cpu usage in the loop when doing multiple conversions

  2. Catch TERM to exit the loop cleanly

  3. Add global variables for the slew rate and re/write timing adjustments
     in the ds2840ut.c file. Add control of these to the digitemp.c code.

  4. Update support for rpm building

X 5. Fix problems using the USB serial port. Not sure what's happening. It
     will sometimes work, most of the time fail. Extending VTIME didn't make
     any noticable difference.

     I changed global_msec_max (controls the time delay for characters in
     the ReadCOM routine). It might be a slight improvement, but still fails
     a considerable percentage of the time.

     Sometimes the DS2480 detection fails, sometimes the search fails. It
     will also sometimes run fine (and quickly).

     Getting somewhere:

     Fails: 17 45 5B 0F 91

     Works: 16 44 5A 00 93

     Sent : 17 45 5B 0F 91

     Once : C1 17 45 5B 0F

     I added a wrapper for DS2480Detect that retries up to 10 times before
     giving up.

     Extending the maximum time to 1.800 or so (1sec + 800mS) also helps it
     run better. Without that it doesn't read the data very well. Without
     the loop on DS2480Detect it doesn't work consistently with the dongle.

     I need to add the delays back in, and see how they effect normal
     operation.

     The problem, it appears, was the usb buffer wasn't being zered before
     being used and an unknown number of bytes can be returned so it wasn't
     actually checking a bit that was set by the data.
     See commit 33422c748e28dc550e31eda63487135537838d00

  6. Add long-argument switches to the program so that counter and switch
     results can be turned on/off. Temperature as well.

  7. Update and review all documents and directions to make sure they are
     current and match the command line.

  8. Update or remove the various helper scripts. Remove hard-coded paths, etc.
