updated to be compatible with mocsy v2 (added Patm argument in call to vars)
modified comment supressing part about not being able to accept arrays
added optGAS (potential vs. in-situ pCO2, fCO2) & changed a0 for KspA pressure corr.
convert fCO2 to pCO2 (uatm)
convert pCO2 to fCO2 (uatm)
solve for carbonate system variables
solve for pH-total alkalinity equation (Munhoven, 2013)
mocsy_GLODAP.py - added optGAS option
makefile - added varsolver.f90 and other test routines
vars.f90 - added optGAS (chooses in-situ vs. potential pCO2, fCO2)