swift234

[gyb] Force Unicode strings in Python 2

All strings are sequences of Unicode characters in Python 3. This is
entirely different than that of Python 2. Python 2's strings were of
bytes. However, Python 2 does have the concept of Unicode strings. This
patch changes the behavior of the file reader to use the same the codecs
module on Python 2 to properly read a string into a unicode string. From
there the strings are meant to be equivalent on 2 and 3. The rest of the
patch just updates the code to natively work with unicode strings.

To test the class `GraphemeClusterBreakPropertyTable`:

    $ python2 utils/gyb --test \
    -DunicodeGraphemeBreakPropertyFile=./utils/UnicodeData/GraphemeBreakProperty.txt \
    -DunicodeGraphemeBreakTestFile=./utils/UnicodeData/GraphemeBreakTest.txt \
    -DCMAKE_SIZEOF_VOID_P=8 \
    -o /tmp/UnicodeExtendedGraphemeClusters.cpp.2.7.tmp \
    ./stdlib/public/stubs/UnicodeExtendedGraphemeClusters.cpp.gyb

    $ python3 utils/gyb --test \
    -DunicodeGraphemeBreakPropertyFile=./utils/UnicodeData/GraphemeBreakProperty.txt \
    -DunicodeGraphemeBreakTestFile=./utils/UnicodeData/GraphemeBreakTest.txt \
    -DCMAKE_SIZEOF_VOID_P=8 \
    -o /tmp/UnicodeExtendedGraphemeClusters.cpp.3.5.tmp \
    ./stdlib/public/stubs/UnicodeExtendedGraphemeClusters.cpp.gyb

    $ diff -u /tmp/UnicodeExtendedGraphemeClusters.cpp.2.7.tmp \
    /tmp/UnicodeExtendedGraphemeClusters.cpp.3.5.tmp

To test the method `get_grapheme_cluster_break_tests_as_UTF8`:

    $ python2 utils/gyb --test \
    -DunicodeGraphemeBreakPropertyFile=./utils/UnicodeData/GraphemeBreakProperty.txt \
    -DunicodeGraphemeBreakTestFile=./utils/UnicodeData/GraphemeBreakTest.txt \
    -DCMAKE_SIZEOF_VOID_P=8 \
    -o /tmp/UnicodeGraphemeBreakTest.cpp.2.7.tmp \
    ./unittests/Basic/UnicodeGraphemeBreakTest.cpp.gyb

    $ python3 utils/gyb --test \
    -DunicodeGraphemeBreakPropertyFile=./utils/UnicodeData/GraphemeBreakProperty.txt \
    -DunicodeGraphemeBreakTestFile=./utils/UnicodeData/GraphemeBreakTest.txt \
    -DCMAKE_SIZEOF_VOID_P=8 \
    -o /tmp/UnicodeGraphemeBreakTest.cpp.3.5.tmp \
    ./unittests/Basic/UnicodeGraphemeBreakTest.cpp.gyb

    $ diff -u /tmp/UnicodeGraphemeBreakTest.cpp.2.7.tmp \
    /tmp/UnicodeGraphemeBreakTest.cpp.3.5.tmp