Log Message:
Update to 64.1

Changelog:
Common Changes

    Unicode 12: 554 new characters, including 4 new scripts and 61 new emoji \ 
characters.
    CLDR 35
        Somali and Javanese data now up to modern level
        Cebuano, Hausa, Igbo, and Yoruba data now up to basic level
        23 additional measurement units
        Many data additions and corrections in many other languages
        The following language has been added to ICU: Cebuano
        This version of ICU does not yet implement the Indic Grapheme Cluster \ 
improvements from CLDR 35.
    New Japanese calendar era from 2019: CLDR and ICU include data for testing \ 
that can be enabled. (ICU #12973, CLDR #10750)
        To enable CLDR new Japanese era placeholder name, set environment \ 
variable (and Java system property for ICU4J) ICU_ENABLE_TENTATIVE_ERA=true \ 
(This was added in ICU 63).
        Support added for Gannen year numbering (using 元 for the first year of \ 
an era) in the Japanese locale Japanese-calendar full, long, and medium formats. \ 
Gannen year support is also automatically added for other non-numeric formats \ 
(those containing other kanji characters such as 年) derived from pattern \ 
skeletons unless specifically overridden. (ICU #20441, CLDR #11843, CLDR #11819)
        We are planning for an ICU 64.2 update in 2019-April which will add the \ 
new Japanese era with its real name.
    ICU 64 now uses "rearguard" TZ data. (Recent versions have used \ 
"vanguard" data with certain overrides.) (ICU-20398)
    ICU data filtering: The ICU4C build accepts an optional filter script that \ 
specifies a subset of the data to be built, with whitelists and blacklists for \ 
locales and for resource bundle paths. (ICU-10923, design doc)
        See this new documentation page: userguide/icu_data/buildtool.md
    MessageFormat has new pattern syntax for specifying the style of a date/time \ 
argument via a locale-independent skeleton rather than a locale-specific \ 
pattern. (ICU-9622)
        Date/time skeletons use the same "::" prefix as number skeletons.
        Example MessageFormat pattern string: "We close on \ 
{closing,date,::MMMMd} at {closing,time,::jm}."
    Many formatting APIs can now output a new type of result object which is-a \ 
FormattedValue (Java & C++), or convertible to a UFormattedValue (C).
        These combine the result strings with easy iteration over FieldPosition \ 
metadata.

ICU4C Specific Changes

    New C++ class LocaleBuilder for building a Locale from subtags, keywords, \ 
and extensions. (ICU-20328)
        Parallel to the existing ICU4J ULocale.Builder class.
    For C++ MeasureUnit instances, there are now additional factory methods that \ 
return units by value, not by pointer-with-ownership. (ICU-20337)
    Various Out-Of-Memory (OOM) issues have been fixed. (ticket query)