Save/restore dbAddr::pfield around callbacks to
avoid corruption if CB forgets to restore.
Need to peak at dbChannel.h during libCom build.
So generate dbCoreAPI.h early, and add extra
-I to source location when compiling dbTrapWrite.c
In some cases the license-identification header was missing,
so I added that as well. Replaced the remaining headers that
specifically identified "Versions 3.13.7 and higher".
Makefiles and the build system were deliberately excluded.
