Added daqd source code doxygen documentation.

doc/top.dox

src/daqd/channel.hh

src/daqd/circ.h

src/daqd/circ.hh

src/daqd/daqd.cc

src/daqd/daqd.hh

src/daqd/edcu.hh

src/daqd/epicsServer.hh

src/daqd/file_checker.hh

src/daqd/filesys.hh

src/daqd/net_listener.hh

src/daqd/net_writer.hh

src/daqd/producer.cc

src/daqd/producer.hh

src/daqd/profiler.hh

src/daqd/trend.hh

src/fe/map.c