Allow very large maximumIntegerDigits.

This allows up to 2 billion to be used as the maximum integer digits,
while keeping the default value at the current 309. This change brings
ICU4J in line with ICU4C limits, which is necessary for correct
implementation of java.text.DecimalFormat on ICU4J.

Bug: 27855939

(cherry picked from commit 86b7d2d760b249da7417f90f09796f3227491aba)

Change-Id: Ic054c0d34e008f7b2ea6a29e6b3d891ecc53d65b
2 files changed