[RFC] enabling C++0x support where available

[Amos Jeffries]

I've located autoconf macros for detecting and enabling C++0x support in 
compilers. Some simple initial tests show it seems to be okay.

With this we can continue to follow the compilers as language features 
are supported. Initially we gain the use of nullptr for extra type 
safety on pointers.

Any objections?

Amos