Better ordinal detection

[rhdunn]

At the moment, tts/context_analysis.cpp detects an ordinal number if a number is followed by st, nd, rd, th. This should be improved to:

1. Restrict the suffixes to their end-digit (e.g. 1 with st) -- or not (to cope with incorrect suffixes like 3st [*]);
2. Support locale-specific suffixes;
3. Support locale-specific variants (e.g. German uses n. to indicate ordinal numbers).

[*] Is this an ordinal or "stones" (weight)?

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