Redefine Exit* macros as variadic macros
Use variadic macros throughout the source
Use arg pointer for VS2010-compat WcaErrorMessage

VS2010 does not define va_copy, but since we aren't actually modifying the va_list we don't need a copy - only a pointer to advance separately from the original.
Merge pull request #45 from heaths/variadic
Fix up build breaks after pull request #45
Fix version warning in SettingsEngineTest project.
Add SettingsEngineTest to all tests.