Change CallGraph print to show the fully qualified name

CallGraph previously would just show the normal name of a function,
which gets really confusing when using it on large C++ projects.  This
patch switches the printName call to a printQualifiedName, so that the
namespaces are included.

Change-Id: Ie086d863f6b2251be92109ea1b0946825b28b49a
llvm-svn: 348950