Move xxd.pl script to core/scripts as its used by other core components like XMLTreeViewer

xxd.pl is used outside the inspector specifically by the core/xml/parser/XMLDocumentParser and 
XMLTreeViewer. Hence moving it to core/scripts for generic usage if required.

R=pfeldman

Review URL: https://chromiumcodereview.appspot.com/23583012

git-svn-id: svn://svn.chromium.org/blink/trunk@157141 bbb929c8-8fbe-4397-9dbb-9b2b20218538