global: Fix spelling mistakes in comments Original work by @andreasschulze and @jsoref

lib-fts: Added maxlen parameter to icu-normalizer. This is needed because the normalization can increase the token's length.

lib-fts: Add prefixing contraction filter. Filters away prefixing contracted words, e.g. "l'homme" -> "homme". Tokens to be filtered must be lower case. Only supports French in this initial version.

lib-fts: Fix comment in fts-filter.h

lib-fts: Added "english-possessive" filter.

lib-fts: Removed unnecessary array.h include from fts-filter.h

lib-fts: Minor code cleanups

lib-fts: Removed filter name macros from fts-filter.h The filters can be directly accessed via their class structs.

lib-fts: Added "lowercase" filter. For now it handles only ASCII characters, but that's enough for our use.

lib-fts: Removed "simple" normalizer. It translated input to titlecase, which wasn't suitable for snowball stemming that wanted lowercase input. Since that doesn't work, there's probably no good for the existence of this (perhaps in future it's replaced by unicode-aware lowercaser).

lib-fts: Changed filter's internal APIs to return error_r directly. It's not very safe to store strings allocated from data stack to any permanent structs.

fts: Improve filter error handling. In lib-fts: Move error storage to the generic filter struct level. Change make_utf8 helper to void also. In fts: Add the error argument to _filter() calls.

fts: Change filter API to be able to return errors Modify fts_filter_filter() to return integer status codes. It returns 1 if a token was returned, 0 if it was filtered away and -1 on error.

lib-fts: Added normalizer-simple for doing normalization without libicu.

lib-fts: Renamed normalizer to icu-normalizer, including the source code.

Initial import for lib-fts. Parts of what this code does was already implemented internally by fts-lucene. lib-fts is intended to be usable for all the FTS backends. The APIs are still going to change a bit, but hopefully not after v2.2.17 release. Mostly written by Teemu Huovila.