Minor, unindent code
Simplify code in StackValue$CollectionElement
Simplify function invocation in ExpressionCodegen

Callee is now generated only when it could be non-trivial, which is only the
case when generating function call in invokeFunction()
Minor, FieldInfo.toString()
Include error type in error message

Everything besides it is almost always useless: descriptor is usually
ERROR_CLASS, declarations are usually nulls because they come from a different
module
Minor refactoring in callable reference codegen

Don't store an extra field for functionDescriptor, since it's available from
the superclass as "callableDescriptor". Store a referenced function descriptor
instead
Support local function references in codegen

 #KT-3704 In Progress
 #KT-1183 In Progress
Add tests on callable references

Object members and accessors for private class members
Support closures in codegen for callable references
Support references to local extensions in codegen
Buildserver auto merge