Fixes UbiquityDotNET#7 - Hardcoded platform string text in Unit tests

- This change simply alters the test for the exception message to verify the part provided by the Llvm.NET library itself, ignoring the trailing part provided by the  BCL, which is subject to Locale differences.
- Appveyor.yml is set to run test in a second locale to help catch any future issues.

appveyor.yml

@@ -36,6 +36,7 @@ after_build:
 
 test_script:
   - ps: .\Invoke-UnitTests.ps1
+  - ps: { Set-Culture fr-FR; .\Invoke-UnitTests.ps1 }
 
 artifacts:
   - path: .\BuildOutput\Nuget\LLvm.NET.*.nupkg

src/Llvm.NETTests/ExpectedArgumentException.cs

@@ -35,13 +35,11 @@ protected override void Verify( Exception exception )
             RethrowIfAssertException(exception);
 
             Assert.IsInstanceOfType(exception, typeof(ArgumentException), WrongExceptionMessage );
-            Assert.AreEqual( ExpectedName, ( ( ArgumentException )exception ).ParamName );
+            var argException = ( ArgumentException )exception;
+            Assert.AreEqual( ExpectedName, argException.ParamName );
             if( !string.IsNullOrWhiteSpace( ExpectedExceptionMessage ) )
             {
-                Assert.AreEqual( $"{ExpectedExceptionMessage}\r\nParameter name: {ExpectedName}"
-                               , exception.Message
-                               , "Could not verify the exception message."
-                               );
+                Assert.IsTrue( exception.Message.StartsWith( ExpectedExceptionMessage, StringComparison.Ordinal ), "Could not verify the exception message." );
             }
         }