Add support to older compilers.


git-svn-id: svn://svn.code.sf.net/p/elmerfem/code/trunk@6865 04224531-1f84-46d8-96ce-875b9e37dce3
fix typo(s).


git-svn-id: svn://svn.code.sf.net/p/elmerfem/code/trunk@6866 04224531-1f84-46d8-96ce-875b9e37dce3
MagnetoDynamicsCalcFields: Fixing a bug in the evaluation of the electric conductivity, enabling JxB computation for stationary cases and enabling the current density computation when the source current is generated internally from a given electric potential (a new keyword Precomputed Electric Potential is here introduced).

git-svn-id: svn://svn.code.sf.net/p/elmerfem/code/trunk@6867 04224531-1f84-46d8-96ce-875b9e37dce3