Added captured types and approximation

CapturedType captures type projection while solving the constraint system.
During the substitution type containing captured types is approximated
to get rid of captured types and (for simple cases) replace them with corresponding type projections.

Note that Array<Array< CapturedType(out Int) >> is (over)approximated by Array<out<Array<out Int>>

See 'Mixed-site variance' by Ross Tate for details.

 #KT-2570 Fixed
 #KT-2872 Fixed
 #KT-3213 Fixed

generators/src/org/jetbrains/jet/generators/tests/GenerateTests.kt

@@ -116,6 +116,7 @@ import org.jetbrains.jet.lang.resolve.java.AbstractJavaTypeSubstitutorTest
 import org.jetbrains.jet.plugin.intentions.declarations.AbstractJoinLinesTest
 import org.jetbrains.jet.codegen.AbstractScriptCodegenTest
 import org.jetbrains.jet.plugin.parameterInfo.AbstractFunctionParameterInfoTest
+import org.jetbrains.jet.resolve.typeApproximation.AbstractCapturedTypeApproximationTest
 import org.jetbrains.jet.psi.patternMatching.AbstractJetPsiUnifierTest
 import org.jetbrains.jet.completion.weighers.AbstractBasicCompletionWeigherTest
 import org.jetbrains.jet.completion.weighers.AbstractSmartCompletionWeigherTest
@@ -167,6 +168,10 @@ fun main(args: Array<String>) {
             model("constraintSystem", extension = "bounds")
         }
 
+        testClass(javaClass<AbstractCapturedTypeApproximationTest>()) {
+            model("capturedTypeApproximation")
+        }
+
         testClass(javaClass<AbstractJetParsingTest>()) {
             model("psi", testMethod = "doParsingTest", pattern = "^(.*)\\.kts?$")
             model("parseCodeFragment/expression", testMethod = "doExpressionCodeFragmentParsingTest", extension = "kt")