Merge remote-tracking branch 'aosp/icu59' into aosp/master.

This upgrades AOSP to ICU 59.

Created by running "git merge aosp/icu59" with the following local
configuration to not touch android_icu4j/ (which is irrelevant as it is
going to be overwritten by generate_android_icu4j.sh), to overwrite all
of icu4c/ and icu4j/ with their contents on the aosp/icu59 branch and
take the union of all changes made to tools/srcgen/ on both branches.

.git/info/attributes:

android_icu4j/resources/** merge=ours
android_icu4j/src/** merge=ours
android_icu4j/** merge=union
icu4*/** merge=theirs
tools/srcgen/** merge=union

.git/config:

[merge "ours"]
        driver = true
[merge "theirs"]
        driver = mv %B %A

Bug: 62410016
Test: ant check
Test: make check
Test: CtsLibcoreOjTestCases
Test: CtsLibcoreTestCases
Change-Id: Iabe48ebcc93f45d555a8f930c7e37fe07cf86121