synchronized C code with R 3.5.1 source, updated ChangeLog and NEWS

[eddelbuettel]

@joshuaulrich If you could casually review -- this had been a 'todo' item for some time. Looks like there weren't too many changes. I compared with R 3.5.1 and carried a few little things over. Yay or nay?

And yes, consider this penance for shipping PRs with ChangeLog or NEWS entries ;-)

[codecov-io]

Codecov Report

Merging #3 into master will increase coverage by 27.64%.
The diff coverage is 70.45%.

@@             Coverage Diff             @@
##           master       #3       +/-   ##
===========================================
+ Coverage   54.67%   82.31%   +27.64%     
===========================================
  Files           6        6               
  Lines        1017      622      -395     
===========================================
- Hits          556      512       -44     
+ Misses        461      110      -351

Impacted Files	Coverage Δ
src/Rstrptime.h	100% <ø> (+75.47%)	⬆️
src/attrib.c	76.47% <50%> (-3.53%)	⬇️
src/datetime.c	80.26% <71.42%> (+13.54%)	⬆️

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[joshuaulrich]

This looks good to me. I looked at the diff ignoring whitespace changes.

[eddelbuettel]

Thanks. It's kinda harder for you as you'd really need a three-way diff between current R, current RApiDatetime, previous RApiDatetime.