ignore datatable.nomatch option with warning

[mattdowle]

2 years since #3585 #3612

[codecov]

Codecov Report

Merging #5108 (24bd9c8) into master (a87c9b0) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #5108   +/-   ##
=======================================
  Coverage   99.54%   99.54%           
=======================================
  Files          76       76           
  Lines       14612    14612           
=======================================
  Hits        14545    14545           
  Misses         67       67           

Impacted Files	Coverage Δ
R/data.table.R	99.94% <ø> (ø)
R/foverlaps.R	100.00% <ø> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update a87c9b0...24bd9c8. Read the comment docs.