RFR: Some build fixes for gcc4.7

[Roman Kennke]

I posted part of this before in hotspot-gc-dev, without any reply yet.
(http://mail.openjdk.java.net/pipermail/hotspot-gc-dev/2012-November/005327.html) 


In any case, here is a more complete patch relating to build failures
with GCC 4.7. It's basically:

- Some more this-> qualifiers in binaryTreeDictionary.cpp (other such
qualifiers have been added before, those here probably slipped through
because they're only in asserts and compiled in debug builds.
- In library_call.cpp some return false should really be return NULL.
Also improves consistency in this code (other return statements in the
same method correctly return NULL).


Ok to go in?

http://cr.openjdk.java.net/~rkennke/gcc47/webrev.00/

Regards,
Roman