StyleCop.MSBuild 6.0.0-beta04

Fixed parsing of switch statements with pattern matching (#154). Fixed parsing of nullable ValueTuple types (#163). Fixed parsing of pattern-matching expressions in LINQ statements (#171). Fixed parsing of ValueTuple types in foreach statements (#179). Fixed parsing of a local function with a namespace-qualified return type (#191). Fixed parsing of interpolated strings containing an "at" symbol (#192). Fixed parsing of variables named "yield" (#195). Fixed parsing of inline "out" variables. Fixed parsing of nullable local functions. Fixed analysis of spacing when the return type of a method is a Task with a ValueTuple result type (#141). Fixed the directory used when searching for a local copy of spelling libraries (#160). Included the local directory when searching for add-ins (#50). Expanded the supported target versions of Visual Studio Professional (#166). Made the "don't care" identifier (i.e. a single underscore character) acceptable (#140).