Contribute a welcome patch to base/utils/main C code

[hturner]

I have been reviewing reports on Bugzilla and have found several where a member of R Core has indicated a patch would be welcome, either by their comments or by adding the HELPWANTED keyword. These bugs are good candidates for contributors to take on at the sprint, though they generally require advanced knowledge of R and/or C. In some cases, the work may extend beyond the sprint, but the sprint can provide an opportunity to get advice from R Core/other experienced contributors.

Bug ID	Level	Topic/Domain	Summary	Language/other
18255	Intermediate	packages	requireNamespace doesn't respect min version when namespace already loaded	R
17871	Intermediate	utils	utils::tar can produce invalid tarballs w/ long usernames/groupnames	R
14354	Advanced	packages	mark non-standard evaluation in local scope to be skipped by codetools	R
16094	Advanced	packages	respect package version restrictions when using ::	R
16311	Advanced	base	set environment variables from env argument	C, Windows
16752	Advanced	base	printing complex numbers in R	C
16856	Advanced	base	addition of millisecond adds a second	C
16034	Advanced	base	iterative unserialization for pairlists	C
17377	Advanced	utils	inconsistent result of getSrcLocation for an S4 method that uses ...	R
18249	Advanced	src/main C code	following Unicode TR31 specification in R	C

Additions or corrections to this list are welcome - note I have not checked if the bugs are current in R-devel.

R Core members commenting on original reports: @mmaechler, @ltierney, @bastistician, @s-u.

[mmaechler]

That's really nice -- thank you @hturner! Very good you also picked some "oldies".
I think that indeed quite a few additions should be possible!