Enable lambdas in all sugar functions

[Enchufa2]

Part of #1365, as discussed in #1370. Takes the idea in #296 that enabled lambdas for sapply, and generalizes it as a variadic result_of that now is applied to lapply, mapply and outer too, enabling lambdas for them too.

Checklist

• Code compiles correctly
• R CMD check still passes all tests
• Preferably, new tests were added which fail without the change
• Document the changes by file in ChangeLog

[kevinushey]

LGTM!

[eddelbuettel]

As discussed over DM as it happened, the reverse depends run for this one tossed up three packages coughing so to be refined or to be patched there.

[Enchufa2]

I think that 8ba2d7b fixes the issue (some, but not all). I dropped that before just because it was giving me problems, and collided somehow with the other specialization. But it works now, so my previous issues were probably due to some intermediate state of the PR.

[Enchufa2]

Stupid mistake... I inadvertently dropped typedef at some point. Now expertsurv, flexsurv and texmex should compile just fine.

[eddelbuettel]

Very nice, and confirmed for those three plus one that was flakey in the last run (and now passed too). Waiting on one new package....

[eddelbuettel]

Thumbs up!