Add experimental feature 'v0.5.0'

libsolidity/ast/ExperimentalFeatures.h

@@ -31,6 +31,7 @@ enum class ExperimentalFeature
 {
 	SMTChecker,
 	ABIEncoderV2, // new ABI encoder that makes use of JULIA
+	V050, // v0.5.0 breaking changes
 	Test,
 	TestOnlyAnalysis
 };
@@ -45,6 +46,7 @@ static const std::map<std::string, ExperimentalFeature> ExperimentalFeatureNames
 {
 	{ "SMTChecker", ExperimentalFeature::SMTChecker },
 	{ "ABIEncoderV2", ExperimentalFeature::ABIEncoderV2 },
+	{ "v0.5.0", ExperimentalFeature::V050 },
 	{ "__test", ExperimentalFeature::Test },
 	{ "__testOnlyAnalysis", ExperimentalFeature::TestOnlyAnalysis },
 };