DataQualityInterfaces: const/mutable fixes
Various minor const
fixes that are flagged by the thread-checker. While this code doesn't run multi-threaded the resulting fixes are still worthwhile in terms of code quality:
-
ConditionsSingleton
: use Meyer's singleton instead of the complicated code to create/delete the singleton - remove usage of
exit
function -
HanUtils
: change tostd::mutex
-
HanOutput
: replacestrtok
withboost::split
(the former modifies the string that is being split!) - remove
mutable
in favor or making visitors non-const