Merge various result_of changes.
- [42234] Reduce header dependencies, from Shunsuke Sogame. Fixes #1535
- [45256] result_of implementation that makes use of C++0x decltype, from Daniel Walker. Fixes #862.
- [48620] Fix result_of to work with const-qualified function pointers. Fixes #1310
- [60052] Remove use of deprecated config macro in result_of.
[SVN r60289]
Daniel James