revset: added lazyset implementation to public revset
Performance Benchmarking:
$ time hg log -qr "first(public())"
...
real 0m1.184s
user 0m1.051s
sys 0m0.130s
$ time ./hg log -qr "first(public())"
...
real 0m0.548s
user 0m0.427s
sys 0m0.118s
Testing that hghave does not crash when checking features $ "$TESTDIR/hghave" --test-features 2>/dev/null