Bug 668 tweak call stack parser

This change was tested on linux x86_64, with a vanilla perl 5.12.5 (freshly compiled) and a distributed perl 5.18.2 (debian). It should fix issue http://sourceforge.net/p/e-p-i-c/bugs/668/.

It does two things:

* match the new debugger stack pattern (apostrophe)
* skip the additional DB::DB stack item which is a duplicate of the one obtained from currentIP (hackish but it works)