uniqlengths doesn't error on 0-length input
Merge branch 'master' into Feature-760
Updated link + minor changes to ?dcast.data.table
forderv(x, na.last=NA) places 0's for NAs always at start now

forderv(c(-Inf, 1, NA), na.last=NA) returned 1,0,2 instead of 0,1,2, for example. This is fixed now.
Fixed an integer overflow segfault case in setRange
Merge branch 'master' into Feature-760
Merge branch 'master' of https://github.com/Rdatatable/data.table
Implements #760. Fast rank for vectors & lists.
Merge branch 'Feature-760'