Add isNormalizedPath to std.path

[dlangBugzillaToGithub]

dechcaudron+issues.dlang reported this on 2018-11-26T19:52:32Z

Transfered from https://issues.dlang.org/show_bug.cgi?id=19438

CC List

• dechcaudron+issues.dlang

Description

Just reporting for completion, fix is already implemented and will provide PR ASAP. I addition to being a useful general-purpose function, it may be used in the `in` contract blocks of functions in std.path expecting a normalized path (see issue 13825).