Create AnonymousFunctionDescriptor

Will be used to check if the descriptor represents a function literal
Minor refactoring in Function/PropertyCodegen

Check if we need to generate code before calling generateMethod()
There were 4 such checks, 2 of them in PropertyCodegen, one in
FunctionCodegen.gen() and one in ClosureCodegen. Every usage except the last
was prepended with the check
Minor refactoring in FunctionCodegen

Combine two nested classes, MethodBounds and LocalVariablesInfo, into one
MethodInfo. Rename some methods. No logic has changed