Added (r:ProjectReferenceEventArgs)

Avoiding 
/fsharpbinding/monodevelop/MonoDevelop.FSharpBinding/FSharpLanguageBinding.fs(84,89): error FS0072: Lookup on object of indeterminate type based on information prior to this program point. A type annotation may be needed prior to this program point to constrain the type of the object. This may allow the lookup to be resolved. 

on (84,89) and (85,93)
Merge pull request #823 from Neftedollar/patch-1

MonoDevelop.FSharpBinding.FSharpLanguageBinding.fs Added (r:ProjectReferenceEventArgs) . Avoid  error FS0072