R dependencies >= 3.3.0

[ben-schwen]

Hi,
I tried to install collapse on R 3.1.0 but compiling went wrong because of

error: ‘SHALLOW_DUPLICATE_ATTRIB’ was not declared in this scope; did you mean ‘DUPLICATE_ATTRIB’?

in multiple files. The reason is that SHALLOW_DUPLICATE_ATTRIB was introduced in 3.3.0

[SebKrantz]

Thanks a lot! I started using some different macros going to 1.7, but I wasn't aware that that decreased backwards compatibility. I would like to stick with SHALLOW_DUPLICATE_ATTRIB though as it is considerably more efficient than DUPLICATE_ATTRIB, particularly for data frames with grouping objects attached. Any particular reason you need to use R 3.1.0? PS: I'll have to submit a patch next week when fixest gets taken off CRAN, so I'll bump up the R dependency then.

[ben-schwen]

Ofc, you can always backport those things, but things become messy when you have to backport a lot.

No particular reason for 3.1.0, I was just surprised to see that >= 2.10 should work and 3.1.0 was the oldest version, I already had installed.