8192927: os::dir_is_empty is incorrect on Windows Summary: Check file names in a directory. It is empty if only the "." and ".." files exist. Use unicode version of windows APIs to handle long path. Reviewed-by: iklam, sspitsyn

^build/
^dist/
^.idea/
nbproject/private/
^webrev
^.src-rev$
^.jib/
\.DS_Store
\.metadata/
\.recommenders/
test/nashorn/script/external
test/nashorn/lib
NashornProfile.txt
.*/JTreport/.*
.*/JTwork/.*