Review and update form parsing logic

[aspnet-hello]

From @Tratcher on Tuesday, August 26, 2014 12:32:12 PM

src/Microsoft.AspNet.WebUtilities/ParsingHelpers.cs has at least one place where it calls char.IsWhiteSpace, but this allows many strange Unicode characters. Review this parsing code and update it to be more accurate.

Copied from original issue: aspnet/HttpAbstractions#119

[aspnet-hello]

From @Tratcher on Monday, December 8, 2014 11:01:47 AM

Query string parsing also uses this code path and needs validation.

[aspnet-hello]

From @davidfowl on Thursday, June 11, 2015 1:05:15 AM

Moving this to beta6

[aspnet-hello]

From @glennc on Monday, August 24, 2015 10:42:48 AM

Is this something that @blowdart should care about?

[aspnet-hello]

From @blowdart on Monday, August 24, 2015 11:37:25 AM

Yea, I'd like to see the PR when it's done, although if you're narrowing to just space and tab I'm not so concerned.

It is worth reviewing where other things call IsWhiteSpace when parsing user input.

[aspnet-hello]

From @muratg on Friday, December 11, 2015 10:11:45 AM

Moving out of V1. We're open to PRs @blowdart :)

[aspnet-hello]

From @blowdart on Friday, December 11, 2015 10:14:15 AM

Yea, we all know you don't want me issuing PRs for anything other than Docs 👍