Add a short date format that's guaranteed to have 4-digit years.

Bug: https://code.google.com/p/android/issues/detail?id=56385
Change-Id: Ie60d8c61aae09358d296654bd30378cbd11eeecb
Merge "Add a short date format that's guaranteed to have 4-digit years."
Merge https://android.googlesource.com/platform/libcore into jb-devel
Merge branch 'jb-devel' of github.com:codefireXperiment/libcore into jb-devel