[Cython] Add saveState/restoreState info to the migration guide

Cherry pick of trunk r2722.

git-svn-id: https://cantera.googlecode.com/svn/cantera/branches/2.1@2726 02a645c2-efd0-11dd-984d-ab748d24aa7e
[Matlab] Fix detection of errors when importing Kinetics

Cast the unsigned return type of newKineticsFromXML to a signed type so that the
check on the Matlab side (which looks at the sign of the return value) can
detect and report errors.

Cherry-pick of trunk r2724.

git-svn-id: https://cantera.googlecode.com/svn/cantera/branches/2.1@2727 02a645c2-efd0-11dd-984d-ab748d24aa7e