[SCons] Setting 'msvc_version' implies 'toolchain=msvc'

git-svn-id: https://cantera.googlecode.com/svn/cantera/trunk@3196 02a645c2-efd0-11dd-984d-ab748d24aa7e
[CTI] Check for correct number of coverage parameters

This detects errors such as providing two sets of coverage parameters as a
single list, rather than as a list with separate entries for each set of
coverage parameters.

git-svn-id: https://cantera.googlecode.com/svn/cantera/trunk@3197 02a645c2-efd0-11dd-984d-ab748d24aa7e