Extend and minor clean H3C dictionary

Based on previous review from Allan feedback, I hope fixes all nits found:

Rename the recently added H3C-HW-Exec-Privilege to H3C-Exec-Privilege
as well as its value names to match with (now-found) effective H3C documentation.

Extend the H3C dictionary but stick with hyphens instead of H3C documentation 
which uses underlines. Does not modify previous use of underline as current
setups might rely on and such a change would cause breakage.