[boost] regex lib: non-greedy repeats w/ match_posix

I noticed that the newest regex version no longer supports non-greedy repeats "+?" in match_posix mode. What was the rationale for this? Is it possible to re-enable non-greedy repeats? As far as I could test, it's not sufficient to modify the syntax check around regex_compile.hpp:1794; regex "a+?" would be valid but matches "aaa" on string "-aaa-" instead of "a". Ralph