Sort methods on Array, List<T>, and other core collections accept null comparers. This is not the case for immutable collections, despite what the doc comments claim. This change fixes the inconsistency buy allowing null comparers being passed to Sort methods of the immutable collections.
Update ImmutableArray`1+Builder.cs
Add directory links for SR.cs files to they appear under the Resources folder in VS.
Merge pull request #143 from weshaggard/LinkSR

Add directory links for SR.cs files so they appear under the Resources folder in VS
Pointed to corefx contrib guide on wiki instead of microsoft/dotnet
Merge pull request #153 from davkean/master

Pointed to corefx contrib guide on wiki instead of microsoft/dotnet
Remove unnecessary allocations

While looking at string allocations in our code base,
I noticed a couple that can be trivially avoided in the XML libraries.
Merge pull request #151 from KrzysztofCwalina/dotnet2

Removes some string-related allocations from XML libraries
Merge pull request #140 from KrzysztofCwalina/dotnet1

Allow null comparer to be passed to ImmutableArray<T>.Sort