[Rd] Bug in order function

[Karl Nordström]

Dear R-devel(opers),

I wanted to draw your attention to a small problem with the order 
function in base. According to the documentation, radix sort supports 
different orders for each argument. This breaks when one of the 
arguments is an object.

Please have a look to this stackoverflow question:

https://stackoverflow.com/questions/39737871/r-order-method-on-multiple-columns-gives-error-argument-lengths-differ

It describes the problem well and suggests a solution.

Although it is a niche case, it's a very easy thing to fix :)

Best regards,

Karl Nordström