use thread-local for C++11, check for standard compliance before checking for compiler extensions
use thread-local for C++11, check for standard compliance before
checking for compiler extensions

JGrothoff/open62541,jpfr/open62541,JGrothoff/open62541,StalderT/open62541,jpfr/open62541,jpfr/open62541,open62541/open62541,open62541/open62541,jpfr/open62541,StalderT/open62541,JGrothoff/open62541,StalderT/open62541,JGrothoff/open62541,open62541/open62541,StalderT/open62541,open62541/open62541