[PATCH] centralised definition for surface pressure

[Jan Schubert]

This patch centralizes the definition for surface pressure, oxygen in
air and defines all such values as plain integers.

It eliminates 11 (!) occurrences of definitions for surface pressure and
also a few for oxygen in air.

It also harmonizes the calculation for EAD, END and EADD for OC and CC
using the new definitons and fixes a bug for EADD OC calculation.

And finally it removes the unneeded variable entry_ead in gtk-gui.c.

Jan

Signed-off-by: Jan Schubert / Jan.Schubert at GMX.li