Enable MSVC warning for thread safety with statics

Clean up a couple of additional issues found while playing with /Wall in MSVC.
Fix issues discovered while evaluating pvs-studio
Merge branch 'develop' of https://github.com/ChaiScript/ChaiScript into develop

Conflicts:
	include/chaiscript/language/chaiscript_common.hpp
	include/chaiscript/language/chaiscript_parser.hpp