A fix in energy.c. Normals are summed now.

Miha Fošnarič

2016-07-11 02d65c3c9baa0e76744ce001c55ec699ab3b956f

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Original written by Dan Kroll in FORTRAN. Code was then largely adapted and commented by Miha Fosnaric-Fosni. Rewritten into C by Samo Penic-Peni, with help of Miha's extensive explanations.