app-i18n/mozc: Version bump (2.20.2673.102).
Upstream migrated from Qt 4 to Qt 5.
"qt4" / "qt5" USE flag renamed to "gui".
"fcitx" USE flag renamed to "fcitx4".
("fcitx5" USE flag will be used to control support for Fcitx 5.)
"handwriting-tegaki" and "handwriting-tomoe" USE flags introduced to select usage
of handwriting recognition model from app-i18n/tegaki-zinnia-japanese or
app-i18n/zinnia-tomoe. "handwriting-tegaki" is enabled by default in accordance
with upstream default for Mozc.
Test suite unrestricted and fixed to build.