Intl Transliterator - polyfill

[voku]

TODO:

• [ ] add more tests - https://github.com/voku/polyfill/blob/intl_transliterator/tests/Intl/Transliterator/TransliteratorTest.php
• [x] not working as expected for PHP <= 5.5
• [ ] some tests did not work on travis-ci (old ICU version)

QUESTIONS:

• [ ] do we need support for "Transliterator->direction"?

reference: https://github.com/voku/portable-ascii/issues/32

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This change is 

[voku]

@nicolas-grekas Hi, here is my first quick try to move the ASCII stuff into a "Transliterator"-polyfill. Maybe you can take a look at this if you have time, thanks.

[stof]

@voku well, debugging why some garbage is returned when running on such old version ?

[voku]

@stof Garbage was return because old PHP versions do not use "UTF-8" encoding by default.

[chx]

Do we want to support the INTL_ICU_VERSION constant?

[nicolas-grekas]

Sorry we didn't catch up on this topic. The amount of work is too high I suppose. Please let me close. Thanks for the PR!