improve the amalgamation procedure; fix a compile issue on msvc
improve the amalgamation procedure; fix a compile issue on msvc

StalderT/open62541,StalderT/open62541,jpfr/open62541,StalderT/open62541,AGIsmail/open62541,AGIsmail/open62541,JGrothoff/open62541,JGrothoff/open62541,open62541/open62541,open62541/open62541,open62541/open62541,jpfr/open62541,bostjanv/open62541,bostjanv/open62541,JGrothoff/open62541,StalderT/open62541,open62541/open62541,jpfr/open62541,JGrothoff/open62541,jpfr/open62541