Fix Tamil bug: use ன instead of ந when not word-initial

[akprasad]

Currently: annam -> அந்நம்
Should be (I think): annam -> அன்னம்

[RamSury]

That change should be made optional - as that is not a phonetic rule that should be applied to the script itself, but a convention in Tamil language (and there are other additional rules which need to be applied to determine when that change won't apply). For example Śeṣanāga should not be transliterated as ஶேஷனாக, it should rather remain ஶேஷநாக, indra should be transliterated as இந்த்ர not இன்த்ர etc.

[akprasad]

@RamSury Thanks for the counsel. Then, I'll leave this as on option, with the default behavior to keep ந.