Test updated: Added check for all cases for covariance/contravariance casts.

--HG--
rename : Tests/SimpleTestCases/CovariantCast_Issue443.cs => Tests/SimpleTestCases/VarianceCast_Issue443.cs
Merge pull request #447 from iskiselev/VarianceTest

Test updated: Added check for all cases for covariance/contravariance casts