Update XML API for Swift 5.1 on Linux

[keith]

With Swift 5.1 corelibs foundation introduced a new module called
FoundationXML and moved all XMLParser related API there. This adds
compatibility for that while still supporting Swift 5.0

[keith]

Ok it looks like Swift 4.x doesn't support allow using the canImport directive. If you want to keep supporting that version I can attempt to wrap this in an #if compiler(>=5.0)

[codecov-io]

Codecov Report

Merging #216 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master     #216   +/-   ##
=======================================
  Coverage   78.56%   78.56%           
=======================================
  Files          13       13           
  Lines        2398     2398           
=======================================
  Hits         1884     1884           
  Misses        514      514

Impacted Files	Coverage Δ
Source/SWXMLHash.swift	82.9% <100%> (ø)	⬆️

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[keith]

I've pushed that to see if CI is happy with it at least

[drmohundro]

@keith thanks for the PR! I was actually about to respond but it looks like you noticed that already. I'm also fine with bumping the SWIFT_VERSION to 5.0 in the .travis.yml file. It might be worthwhile to bump the major version if it will be using 5+ specific features, but I'm fine with that. The versioning has more or less followed the Swift version numbers anyway.

[keith]

Up to you! But if this iteration works I guess you can decide to do that independently of adding 5.1 support

[drmohundro]

Yep, still doesn't like that flag either...

Compile Swift Module 'SWXMLHash' (3 sources)
/home/travis/build/drmohundro/SWXMLHash/Source/SWXMLHash.swift:33:5: error: unexpected platform condition (expected 'os', 'arch', or 'swift')
#if compiler(>=5.1)
    ^

I'm happy to make the change tomorrow or let you if you if you can get to it sooner.

[drmohundro]

LGTM!

[keith]

Thanks!

[drmohundro]

I'll get 5.0.0 tagged/released shortly. Thanks again for the contribution!