Fix badly formed module paths on Windows

[julian-maughan]

This addresses the issue raised in #1358.

It ensures 'required' modules have the expected path, i.e. require("/apps/Call") instead of require("/apps\\Call").

[anddoutoi]

Ran into a simialar issue where both browserify -r ./foo/bar.js and browserify -r ./foo/bar.js:./foo/bar.js both returned some weird mix of absolute unix path and escaped windows path: /foo\\bar.js.

Leaving out .js in the target part works though, e.g. browserify -r ./foo/bar.js:./foo/bar returns ./foo/bar

[TheSharpieOne]

lgtm

[ghost]

Thanks for the patch, merged in 12.0.2.