Added options to the UNITS keyword to allow moles of solid

reactants to be interpreted as moles per liter of WATER or
 	moles per liter of ROCK:
	
	UNITS
		-equilibrium_phases   ROCK
		-exchange             ROCK
		-surface              WATER
		-solid_solution       WATER
		-kinetics             WATER
		-gas_phase            WATER
		
	By default, the number of moles of solid reactants are
	interpreted as per liter of water. Using the ROCK option,
	PHAST interprets the number of moles of solid
	reactants obtained from the initial PHREEQC calculation
	as per liter of rock. 
	
	Note that an initial PHREEQC calculation is made at the
	beginning of a PHAST run. During this calculation all 
	reaction calculations interpret the concentration of solid
	reactants as simply moles. (When a solution is reacted with
	the solids, the solution contains a mass of water, which is
	usually 1 kg, but not necessarily.) It is only when initial 
	conditions are subsequently distributed in the PHAST calculation 
	that solid reactants are scaled. If the units are WATER, t
	here is no scaling and the number of moles of solids is the 
	number of moles per liter of water. If the units are ROCK, 
	the number of moles of a solid reactant	is multiplied by 
	(1-phi)/phi, where phi is the porosity in the cell receiving 
	the initial condition, to arrive at the	number of moles of 
	solid reactant per liter of water. 
	
	The addition of the ROCK option is motivated by the possibility
	of a domain with a distribution of porosities. In this case, 
	the number of moles of solid reactants per liter of water--
	the units used by PHAST--also vary spatially. By using the 
	ROCK option, a constant rock composition can be defined and 
	the factor (1-phi)/phi is used to scale the number of moles 
	of solid reactant to obtain the number of moles per liter 
	of water in each cell.

git-svn-id: svn://136.177.114.72/svn_GW/phreeqcpp/trunk@3902 1feff8c3-07ed-0310-ac33-dd36852eb9cd

cxxMix.h

@@ -36,6 +36,14 @@ class cxxMix:public cxxNumKeyword
 			mixComps[n] = f;
 		}
 	};
+	void multiply(double f)
+	{
+		for (std::map < int, double >::iterator it = this->mixComps.begin();
+			it != this->mixComps.end(); it++)
+		{
+			it->second *= f;
+		}
+	};
 
 	std::map < int, double >*comps()
 	{