Add more language code abbreviations for IN

[rajeeshknambiar]

Add more Indian language abbreviations including Assamese, Bengali, Tamil etc.

[khaledhosny]

Are all these languages spoken only in India?

[rajeeshknambiar]

To the best of my knowledge - yes, with the exception of Panjabi (pa) and Urdu (ur) - they are also spoken in Pakistan.
For my understanding - does it mean that if a language has more than one locale associated, it shall only have short abbreviation code?

[khaledhosny]

For my understanding - does it mean that if a language has more than one locale associated, it shall only have short abbreviation code?

Yes, until we fix how hyphenation and spelling dictionaries are loaded so that if ab_CD is not found we check for ab, which will make the whole alternate tag thing redundant.