ICU-13513 Merging trunk to branch

X-SVN-Rev: 40825

diff --cc icu4j/main/classes/core/src/com/ibm/icu/impl/number/DecimalQuantity.java
Simple merge

diff --cc icu4j/main/classes/core/src/com/ibm/icu/impl/number/DecimalQuantity_AbstractBCD.java
Simple merge

diff --cc icu4j/main/classes/core/src/com/ibm/icu/impl/number/MutablePatternModifier.java
Simple merge

diff --cc icu4j/main/tests/core/src/com/ibm/icu/dev/impl/number/DecimalQuantity_SimpleStorage.java
Simple merge