Add support of internal arguments for language feature settings

Arguments are passed in form '-XXLanguage:+LanguageFeatureName' for enabling
LanguageFeature.LanguageFeatureName, and '-XXLanguage:-LanguageFeatureName'
for disabling.

Note that they do override other settings, including 'language-version'
or extra ('-X') args.

compiler/testData/cli/jvm/internalArgEnableLanguageFeature.args

@@ -0,0 +1,6 @@
+$TESTDATA_DIR$/inlineClass.kt
+-d
+$TEMP_DIR$
+-language-version
+1.2
+-XXLanguage\:+InlineClasses