RFE: Remove unncessary volatile usages in java.math.BigDecimal and related classes

In java.lang.BigDecimal implementation, we seem to declare several memebers such as "precision, stringCache" as "volatile". Even though volatile read is only slightly slower than normal read, but volatile write is much slower than normal store/write. Intel folks found that by removing the volatile uses, they noticed some meaningful differences on some benchmarks such as derby inside SPECjvm2007.