Updated vi_VN locale file

[Le Hong Boi]

LC_MONETARY
change the value of frac_digits and int_frac_digits keywords to 0. The
value of Vietnamese dong is too small that we do not need fractional
digits.
LC_TIME
correct the name of the first month of the year in mon keyword.
change the characters to precompound in day and mon keywords.
Precompound characters are rendered better.
LC_MESSAGE
change yesexpr and noexpr keywords to Vietnamese instead of y/n.

Lê Hồng Bội
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vi_VN
Description: Text document