The first two patches deal with issues with 'this' capture; we were 
inappropriately capturing 'this' for uses of static members and forming 
pointers to members, and for uses in unevaluated context.  The last 
patch avoids a crash from recursive use of dfs_walk when instantiating a 
class with virtual functions using a local class whose scope involves a 
qualified-id.

Tested x86_64-pc-linux-gnu, applying to trunk.