Fixed MSVC being upset with use of trailing return type in non parameter taking function.
Fixed use of range for which VS2010 can't cope with.
Regenerated docs to include Paul's new docs plus my additional API use examples.
Fixed up lots of minor breakage on mingw.
Added async repeat of async enumeration on Windows to cope with maxitems=1.

With that, issue #12 (Add fast directory enumeration) ought to be finished.