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/inlineClass.kt

@@ -0,0 +1 @@
+inline class Foo(val x: Int)

compiler/testData/cli/jvm/internalArgDisableLanguageFeature.args

@@ -0,0 +1,6 @@
+-language-version
+1.3
+-XXLanguage\:-InlineClasses
+$TESTDATA_DIR$/inlineClass.kt
+-d
+$TEMP_DIR$

compiler/testData/cli/jvm/internalArgDisableLanguageFeature.out

@@ -0,0 +1,14 @@
+warning: ATTENTION!
+This build uses internal compiler arguments:
+
+-XXLanguage:-InlineClasses
+
+This mode is strictly prohibited for production use,
+as no stability/compatibility guarantees are given on
+compiler or generated code. Use it at your own risk!
+
+warning: language version 1.3 is experimental, there are no backwards compatibility guarantees for new language and library features
+compiler/testData/cli/jvm/inlineClass.kt:1:1: error: the feature "inline classes" is experimental and should be enabled explicitly
+inline class Foo(val x: Int)
+^
+COMPILATION_ERROR

compiler/testData/cli/jvm/internalArgEmptyFeatureName.args

@@ -0,0 +1,4 @@
+$TESTDATA_DIR$/inlineClass.kt
+-d
+$TEMP_DIR$
+-XXLanguage\:+

compiler/testData/cli/jvm/internalArgEmptyFeatureName.out

@@ -0,0 +1,14 @@
+warning: ATTENTION!
+This build uses internal compiler arguments:
+
+-XXLanguage:+
+
+This mode is strictly prohibited for production use,
+as no stability/compatibility guarantees are given on
+compiler or generated code. Use it at your own risk!
+
+warning: empty language feature name for internal argument '-XXLanguage:+'
+compiler/testData/cli/jvm/inlineClass.kt:1:1: error: the feature "inline classes" is experimental and should be enabled explicitly
+inline class Foo(val x: Int)
+^
+COMPILATION_ERROR

compiler/testData/cli/jvm/internalArgEnableLanguageFeature.args

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

compiler/testData/cli/jvm/internalArgEnableLanguageFeature.out

@@ -0,0 +1,11 @@
+warning: ATTENTION!
+This build uses internal compiler arguments:
+
+-XXLanguage:+InlineClasses
+
+This mode is strictly prohibited for production use,
+as no stability/compatibility guarantees are given on
+compiler or generated code. Use it at your own risk!
+
+warning: following manually enabled features will force generation of pre-release binaries: InlineClasses
+OK

compiler/testData/cli/jvm/internalArgMissingModificator.args

@@ -0,0 +1,4 @@
+$TESTDATA_DIR$/inlineClass.kt
+-d
+$TEMP_DIR$
+-XXLanguage\:InlineClasses

compiler/testData/cli/jvm/internalArgMissingModificator.out

@@ -0,0 +1,14 @@
+warning: ATTENTION!
+This build uses internal compiler arguments:
+
+-XXLanguage:InlineClasses
+
+This mode is strictly prohibited for production use,
+as no stability/compatibility guarantees are given on
+compiler or generated code. Use it at your own risk!
+
+warning: incorrect internal argument syntax, missing modificator: -XXLanguage:InlineClasses
+compiler/testData/cli/jvm/inlineClass.kt:1:1: error: the feature "inline classes" is experimental and should be enabled explicitly
+inline class Foo(val x: Int)
+^
+COMPILATION_ERROR

compiler/testData/cli/jvm/internalArgUnrecognizedFeature.args

@@ -0,0 +1,4 @@
+$TESTDATA_DIR$/inlineClass.kt
+-d
+$TEMP_DIR$
+-XXLanguage\:+UnknownFeature

compiler/testData/cli/jvm/internalArgUnrecognizedFeature.out

@@ -0,0 +1,14 @@
+warning: ATTENTION!
+This build uses internal compiler arguments:
+
+-XXLanguage:+UnknownFeature
+
+This mode is strictly prohibited for production use,
+as no stability/compatibility guarantees are given on
+compiler or generated code. Use it at your own risk!
+
+warning: unknown language feature 'UnknownFeature' in passed internal argument '-XXLanguage:+UnknownFeature'
+compiler/testData/cli/jvm/inlineClass.kt:1:1: error: the feature "inline classes" is experimental and should be enabled explicitly
+inline class Foo(val x: Int)
+^
+COMPILATION_ERROR

compiler/testData/cli/jvm/internalArgWrongPrefix.args

@@ -0,0 +1,4 @@
+$TESTDATA_DIR$/inlineClass.kt
+-d
+$TEMP_DIR$
+-XX:+InlineClasses

compiler/testData/cli/jvm/internalArgWrongPrefix.out

@@ -0,0 +1,5 @@
+warning: flag is not supported by this version of the compiler: -XX:+InlineClasses
+compiler/testData/cli/jvm/inlineClass.kt:1:1: error: the feature "inline classes" is experimental and should be enabled explicitly
+inline class Foo(val x: Int)
+^
+COMPILATION_ERROR

compiler/testData/cli/jvm/internalArgumentOverrideExtraArgument.args

@@ -0,0 +1,5 @@
+$TESTDATA_DIR$/legacySmartCastsAfterTry.kt
+-d
+$TEMP_DIR$
+-XXLanguage\:+SoundSmartCastsAfterTry
+-Xlegacy-smart-cast-after-try

compiler/testData/cli/jvm/internalArgumentOverrideExtraArgument.out

@@ -0,0 +1,13 @@
+warning: ATTENTION!
+This build uses internal compiler arguments:
+
+-XXLanguage:+SoundSmartCastsAfterTry
+
+This mode is strictly prohibited for production use,
+as no stability/compatibility guarantees are given on
+compiler or generated code. Use it at your own risk!
+
+compiler/testData/cli/jvm/legacySmartCastsAfterTry.kt:8:9: error: only safe (?.) or non-null asserted (!!.) calls are allowed on a nullable receiver of type String?
+    some.length
+        ^
+COMPILATION_ERROR