MSRV bump to rust 1.48 in version 0.1.54

[astraw]

From @djc #91 (comment):

So chrono 0.4 is still the active release branch, and is currently still maintaining an MSRV of 1.38. We're working on 0.5 (which requires 1.48) but that's not very close to being done. Would it be a big ask to request that this project keeps its MSRV at 1.38 for a bit longer?

Oh, I wasn't considering that we would exceed chrono's MSRV with release 0.1.54 that we just made yesterday. I apologize that I missed that. By the appearance of this comment, I am guessing this is an actual problem? I am pleased with removing so much unsafe code on Windows with release 0.1.54, so I would like to balance the problem of increased MSRV with the benefit of less unsafe.

On one hand, we could make a 0.1.55 release which is identical to 0.1.53 except in version number. We don't need to yank 0.1.54 as there's no security problem with it. (It just increases the MSRV.)

Alternatively, where old rust is required, iana-time-zone could be pinned to version <=0.1.53 . This would be more burden on the maintainers of software that requires old rust.

I definitely think this issue merits some discussion, so I've opened the new issue on it. @Kijewski your input is also welcome here.

[djc]

Hah, I made an issue in chrono as well with a bit more context, let's discuss there?

chronotope/chrono#995

[astraw]

Yes. Closing this here for now.