Add current_path() setter, !#800, change form of some includes in response to bug report !#600
Add recursive_directory_iterator test cases to convenience_test.cpp, fix !#1061 plus a pop() bug detected by new tests
Fix !#1073. Also reinstate changes from two prior versions dropped inadvertently by revision 35823.
Get rid of non_posix_equivalent, fix Jamfiles, fix Linux typos, refactor so basic_filesystem_error::what() works on compilers that screw up member specializations