RFR (XS) 8238909: x86_32 fails gtest:power_of_2

[Aleksey Shipilev]

Bug:
  https://bugs.openjdk.java.net/browse/JDK-8238909

Fix:
  https://cr.openjdk.java.net/~shade/8238909/webrev.01/

The problem here is is_power_of_2(intptr_t), which truncates int64_t on x86_32, and replies "false"
on large power-of-two values. is_power_of_2_long(jlong) is awkward, but alternatives seem worse:
 *) "LP64_ONLY(is_power_of_2(value)) NOT_LP64(is_power_of_2_long(value))" looks worse;
 *) Overloading is_power_of_2(int64_t) quickly runs afoul of ambiguities on the platforms I tried;
 *) Specializing the whole thing for 8-byte types seems to invite even more template madness;

Testing: affected test on {x86_64, x86_32}; jdk-submit

-- 
Thanks,
-Aleksey