[boost] [range] Request to merge minor small defect fixes

Please may I merge some very small defect fixes for Boost.Range, and an additional test? The defect fixes are to improve return types consistency. I would like to get the interface correct for the first release of the merged RangeEx code. I have also added a test case that checks the use of non-member functions as functors and explicitly tests chaining of Range Adaptors. I believe this provides appreciably better visibility of the state of the library on the various compilers. These changes have been passing tests on the trunk for several days. The changes are also extremely low impact as they are in the new Range code that is not yet used within the rest of the Boost libraries. Thanks, Neil Groves