Simplify the H2O special-casing

re #1119

AUTO appears to be doing the right thing...
(even if that baffles me, given the state of the Kernel sources,
unless they flip some switches at compile time
[NTX_WFM_MODE_OPTIMIZED_REAGL / NO_AUTO_REAGL_MODE] ...)

Anyway, that's what nickel does, so follow its lead ;).
Merge pull request #1130 from NiLuJe/master

Simplify the H2O special-casing