[Gerald Combs <gerald@xxxxxxxxxxxxx>]

In order to speed up compile time, I've added a cache to
make-dissector-reg.py (the script used to generate register.c).  When
you update a dissector and recompile, it _should_ pull the registration
data for unchanged dissectors from its cache, thereby speeding up
compilation time.  On my home machine this shortens recompilation times
by about 20 to 30 seconds.

Let me know if there are any problems.