CJ fails with proper error msg

[jangorecki]

Closes #2636

[MichaelChirico]

I would make the error message more helpful to users, e.g.

stop("Input would result in ", nrow, " rows, which exceeds ", 
     .Machine$integer.max, ", the largest storable integer on this machine ",
     "(as dictated by '.Machine$integer.max').")

[codecov-io]

Codecov Report

Merging #2641 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #2641      +/-   ##
==========================================
+ Coverage   93.16%   93.17%   +<.01%     
==========================================
  Files          61       61              
  Lines       12166    12169       +3     
==========================================
+ Hits        11335    11338       +3     
  Misses        831      831

Impacted Files	Coverage Δ
R/setkey.R	93.86% <100%> (+0.06%)	⬆️

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[mattdowle]

Good idea.