Fix openmp in MultiParticle.h file
Fix openmp in MultiParticle.h file

GOMC-WSU/GOMC,GOMC-WSU/GOMC_Serial,GOMC-WSU/GOMC,GOMC-WSU/GOMC_Serial,GOMC-WSU/GOMC,GOMC-WSU/GOMC_Serial,GOMC-WSU/GOMC,GOMC-WSU/GOMC