Re-implement around epicsTimeStamp (C API)
with class epicsTime becoming a wrapper.
Prefer epicsInt64 arithmetic.
Remove opaque struct l_fp (NTP time conversion)
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.