[RFC][DISCUSSION] debug_backtrace alternative as an array of StackFrame objects

Hi internals, following recently added alternative to token_get_all() in form of a dedicated class PhpToken I've made a similar proposal for collecting stack traces by introducing StackFrame::getTrace() and StackFrame which replaces array with keys and values known from debug_backtrace(). To compete with easier adoption StackFrame implements ArrayAccess giving identical API to debug_backtrace(). A test script with deep recursion up to 1M frames uses 50% less memory than debug_backtrace(). The RFC is described here https://wiki.php.net/rfc/stack-frame-class It includes implementation of PoC and tests. Cheers, Michał Marcin Brzuchalski