RFR: 8241920: G1: Lazily initialize OtherRegionsTable::_coarse_map

[Claes Redestad]

Hi,

initializing OtherRegionsTable::_coarse_map lazily allows for a small
startup and footprint improvement, with no measurable cost to GC
collection times.

Webrev: http://cr.openjdk.java.net/~redestad/8241920/open.00/
Bug:    https://bugs.openjdk.java.net/browse/JDK-8241920

Thanks!

/Claes