Use language-version option in tests instead of excluding them

buildSrc/plugins/src/main/groovy/org/jetbrains/kotlin/KonanTest.groovy

@@ -669,6 +669,12 @@ class RunExternalTestGroup extends RunStandaloneKonanTest {
             }
         }
 
+        def languageVersion = findLinesWithPrefixesRemoved(text, "// LANGUAGE_VERSION: ")
+        if (languageVersion.size() != 0) {
+            flags.add("-language-version")
+            flags.add(languageVersion.first())
+        }
+
         def experimentalSettings = findLinesWithPrefixesRemoved(text, "// !USE_EXPERIMENTAL: ")
         if (experimentalSettings.size() != 0) {
             experimentalSettings.forEach { line ->
@@ -849,12 +855,6 @@ fun runTest() {
             return false
         }
 
-        def version = findLinesWithPrefixesRemoved(text, '// LANGUAGE_VERSION: ')
-        if (version.size() != 0 && version.contains("1.2")) {
-            // Support tests for 1.3 and exclude 1.2
-            return false
-        }
-
         def targetBackend = findLinesWithPrefixesRemoved(text, "// TARGET_BACKEND")
         if (targetBackend.size() != 0) {
             // There is some target backend. Check if it is NATIVE or not.