RFR(XS): 8149973: Optimize object alignment check in debug builds.

[Dmitry Dmitriev]

Hello,

Please, review small optimization to the object alignment check in the 
debug builds. In this fix I replace division by MinObjAlignmentInBytes 
to bitwise AND operation with MinObjAlignmentInBytesMask, because 
MinObjAlignmentInBytes is a power of two. Suggested construction already 
used in MacroAssembler, e.g. 
hotspot/src/cpu/x86/vm/c1_MacroAssembler_x86.cpp).

JBS: https://bugs.openjdk.java.net/browse/JDK-8149973
webrev.00: http://cr.openjdk.java.net/~ddmitriev/8149973/webrev.00/ 
<http://cr.openjdk.java.net/%7Eddmitriev/8149973/webrev.00/>
Testing: jprt, hotspot_all

Thanks,
Dmitry