6688799: Second fix for Guarantee failure "Unexpected dirty card found"
Summary: Expand cardtable without committing over existing regions.
Reviewed-by: apetrusenko
6681796: hotspot build failure on gcc 4.2.x (ubuntu 8.04) w/ openjdk 6
Summary: Fixed the cast from char* to const char* and tried to use const char* as much as possible
Reviewed-by: never, kamg
Contributed-by: xiaobin.lu@sun.com