no need to include alloca.h if gcc is used
no need to include alloca.h if gcc is used

(cherry picked from commit 3b1c0305c536607d578512b64a477e140e0aab56)

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