support portable pdb files

[ctaggart]

Portable pdb files are designed specifically for .NET. The spec is now 1.0 and an implementation ships with Roslyn for Visual Studio 2015 Update 1. The new format is cross platform and several times smaller, making it practical to include in the nupkgs #294. This should take care of the CoreCLR status issue of Enable CoreCLR debugging of F#.

Microsoft.DiaSymReader.PortablePdb exists to provide compatibility to the existing Windows debugging tools that build on top of that COM API.

I am advocating that the old PDB support be dropped to makes things simpler and easier to maintain.

[enricosada]

No need to deprecate pdb, just add the portable pdb, the user can choose using a compiler flag.
After portable pdb works, can be the default for new projects ( in project templates )

Btw yes, i think portable pdb is not a coreclr only issue, should be send to master, and merged in coreclr later, so we can use it with desktop clr ( .net 4.0 )

[Alxandr]

I agree with @ctaggart that the old PDBs should be deprecated/dropped.

[dsyme]

I expect we won't drop for a while, as the compiler will still need to be used for .NET Framework compilation on back-target .NET implementations (4.0-4.6) for several years to come. There may be a "compat" compiler that is used to achieve this.

But getting the new format implemented would be wonderful.

[ctaggart]

I don't think the new pdb format is tied to a .NET Framework version. There is a Microsoft.DiaSymReader.PortablePdb that is being worked on to allow existing Windows debuggers to work with the new format. It would be good to define the test cases for switching.

[KevinRansom]

Portable pubs will be generated by the coreclr version of the compiler. It is the next but one thing on my list.

[ctaggart]

Awesome! Looking forward to it. I am going to try to get SourceLink working with them this month.

[dsyme]

This has been implemented