StringComparison code fix provider generates invalid code

[bgrainger]

The expression !a.Equals(b) is converted to !a == b, which is invalid C#. The suggested replacement should be a != b.

Test case to repro:

		[Test]
		public void DiagnoseAndFixNegatedStringEquals()
		{
			const string program = @"using System;
namespace ConsoleApplication1
{
	class Program
	{
		static void Main(string[] args)
		{
			GC.KeepAlive(!""a"".Equals(""b""));
		}
	}
}
";
			var expected = new DiagnosticResult
			{
				Id = OverloadWithStringComparisonAnalyzer.AvoidStringEqualsDiagnosticId,
				Message = "Use operator== or a non-ordinal StringComparison.",
				Severity = DiagnosticSeverity.Warning,
				Locations = new[] { new DiagnosticResultLocation("Test0.cs", 8, 22) },
			};

			VerifyCSharpDiagnostic(program, expected);

			const string fix1 = @"using System;
namespace ConsoleApplication1
{
	class Program
	{
		static void Main(string[] args)
		{
			GC.KeepAlive(""a"" != ""b"");
		}
	}
}
";
			VerifyCSharpFix(program, fix1, 0);

			const string fix2 = @"using System;
namespace ConsoleApplication1
{
	class Program
	{
		static void Main(string[] args)
		{
			GC.KeepAlive(!""a"".Equals(""b"", StringComparison.OrdinalIgnoreCase));
		}
	}
}
";
			VerifyCSharpFix(program, fix2, 1);
		}