Please backport ibus-typing-booster 2.9.3-1 (universe) from groovy

Please backport ibus-typing-booster 2.9.3-1 (universe) from groovy to xenial, bionic, focal.

Reason for the backport:
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Ibus-typing-booster is a predictive input method and predicts complete words based on context and partial input. One can then simply select the desired word from a list of suggestions and improve one's typing speed and spelling. Mike Fabian seems to be the driving upstream author/maintainer.

ibus-typing-booster has just been packaged for Debian/Ubuntu, but the tool has been around for several years. An ITP bug (<https://bugs.debian.org/729851>) was filed in 2013, but the package was still uploaded to Debian only recently. It has been packaged for Fedora and OpenSUSE for quite a while. This backport proposal is an attempt to repair the damage...

Unlike many input methods, ibus-typing-booster is not for Chinese or Japanese but for basically all other languages. So it should be potentially interesting for a large user base.

Testing:
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Mark off items in the checklist [X] as you test them, but please leave the checklist so that backporters can quickly evaluate the state of testing.

* focal:
[ ] Package builds without modification
    Almost. Changed debhelper-compat to 12.

[X] ibus-typing-booster installs cleanly and runs

* bionic:
[ ] Package builds without modification
    Not quite. In addition to the modification in focal, a couple of
    adjustments were made in d/rules and d/control to fit the older
    ibus version, including configuring with libexecdir=/usr/lib/ibus

[X] ibus-typing-booster installs cleanly and runs

* xenial:
[ ] Package builds without modification
    Not quite. In addition to the modification in bionic, the
    debhelper build-dep was set to >=10 and d/compat was added.

[X] ibus-typing-booster installs cleanly and runs

No reverse dependencies