Fix #492 - use ConvILTypeRefUnadjusted not ConvILTypeRef

[latkin]

• Bug number Runtime error with SqlEntityConnection TP under VS 2015 RC and F# 3.1 #492
• Customer scenario Runtime crash in user code (dynamic assembly load failure) due to bad codegen. This is a regression. Occurs when downtargeting to F# 3.1 and using any query expression against the SQL Entity type provider (or other type providers that use static linking in a similar way).
• Fix description

Use correct API when encoding quoted assembly references. ConvILTypeRefUnadjusted properly handles the case where the reference is statically linked. ConvILTypeRef does not.

These two used to be a single API. They were split in 640db00 and it was a simple oversight that the wrong one was wired up here.

• Testing done
  We have private tests which cover these type providers, they were simply never run in a cross-version configuration. That's frustrating, as cross-version testing was automated recently with Automated cross-targeting testing #446. Running those tests, the bug would have been found a month ago. With the fix, they all pass.

[latkin]

@dsyme there is now only one direct use of ConvILTypeRef, below on line 978. Can you take a second look and confirm that this call is correct?

[dsyme]

There would certainly be no harm in adjusting that one for uniformity, but its harmless either way - the case is only used for the built-in primitive types like these: https://github.com/Microsoft/visualfsharp/blob/fsharp4/src/fsharp/FSharp.Core/prim-types-prelude.fsi#L73 as mentioned here https://github.com/Microsoft/visualfsharp/blob/275b832e9dd1a4bd64ed3accd218384b901be1d2/src/fsharp/tast.fs#L3681. I think this specific case is probably only used for nativeptr if at all.

[latkin]

This guy has also been approved