ast: improved lively.ast.acorn.printAst (allows to print source and node positions as well)
debugging: rewriting adds ast position of "debugger" unwind exception for finding resume node
debugging: add the correct ast positions to computation results when rewriting
ast: acorn copy remembers source attribute
debugging: cleanup for rewriting functions
debugging: computing the "pc" (currently ast node where execution stopped on unwind)
debugging: declaring inner functions that appear in a rewritten function also as rewritten (via __createClosure)