RFR(xs): 8241726: Re-enable gtest for BitMap::count_one_bits()

[Thomas Stüfe]

Hi,

please review this small patch. It adds a gtest to test the
BitMap::count_one_bit() variants, including the new form which works over
arbitrary bit ranges.

That and this gtest were introduced with [1] but the gtest showed errors
and I removed it with [2]. It is now fixed and retested on all our
platforms, including big endian and 32bit machines. So it can be re-added.

Issue: https://bugs.openjdk.java.net/browse/JDK-8241726
Webrev:
http://cr.openjdk.java.net/~stuefe/webrevs/8241726-reenable-gtest-for-count-one-bits/webrev.00/webrev/

Thanks, Thomas

[1] https://bugs.openjdk.java.net/browse/JDK-8241581
[2] https://bugs.openjdk.java.net/browse/JDK-8241723