Zeroconf cleanup, mostly making it possible to compile it out.
Update license date on all files. No functional changes.
Be more careful with enums, which are not just aliases for integers in
C++. Most importantly, use gdp_cmd_t instead of various int types for
commands and acks.
Update licenses to 2017.
A bit more cleanup on Zeroconf code (mostly formatting).
Rename globals and structs, get rid of mixed whitespace, and break up long lines
Update license. No code changes.
Include copyright in all files. There are scripts to do bulk
replacement of the copyright if desired.
intergrated zeroconf into main gdp lib