RFR: 8264161: BigDecimal#stripTrailingZeros can throw undocumented ArithmeticException

[Joe Darcy]

While some of the existing text in BigDecimal could be read as implying exponent overflow/underflow will throw an ArithmeticException, it is reasonable to simply state that explicitly.

The next text is meant to cover the usage of the checkScale family of methods.

I'll reflow the existing paragraph once the text is agreed to.

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Commit messages:
 - 8264161: BigDecimal#stripTrailingZeros can throw undocumented ArithmeticException

Changes: https://git.openjdk.java.net/jdk/pull/3204/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3204&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8264161
  Stats: 7 lines in 1 file changed: 5 ins; 1 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3204.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3204/head:pull/3204

PR: https://git.openjdk.java.net/jdk/pull/3204