Revert breaking changes and add new GenV* interfaces#68

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ktnyt wants to merge 2 commits intosatori:masterfrom ktnyt:master

+84-25

Commits on Jan 5, 2018

Revert breaking changes and add new GenV* interfaces
Kotone Itaya
committed

Commits on Jan 6, 2018

Modify NewV{1,2,4} to panic on error as in the original implementation
ktnyt
committed