Boost: set C++ flags in user.jam instead of cxxflags
Boost: set C++ flags in user.jam instead of cxxflags

Fix issue #174

jkhoogland/hunter,NeroBurner/hunter,daminetreg/hunter,tatraian/hunter,dmpriso/hunter,fwinnen/hunter,madmongo1/hunter,pretyman/hunter,xsacha/hunter,dan-42/hunter,NeroBurner/hunter,mchiasson/hunter,ingenue/hunter,zhuhaow/hunter,vdsrd/hunter,fire-hunter/hunter,dvirtz/hunter,ThomasFeher/hunter,jkhoogland/hunter,tatraian/hunter,madmongo1/hunter,ErniBrown/hunter,stohrendorf/hunter,vdsrd/hunter,pretyman/hunter,designerror/hunter,dan-42/hunter,ikliashchou/hunter,NeroBurner/hunter,shekharhimanshu/hunter,lucmichalski/hunter,ikliashchou/hunter,RomanYudintsev/hunter,ingenue/hunter,ingenue/hunter,stohrendorf/hunter,akalsi87/hunter,NeroBurner/hunter,Knitschi/hunter,caseymcc/hunter,ErniBrown/hunter,pretyman/hunter,isaachier/hunter,dmpriso/hunter,lucmichalski/hunter,RomanYudintsev/hunter,mchiasson/hunter,x10mind/hunter,ledocc/hunter,dvirtz/hunter,ulricheck/hunter,headupinclouds/hunter,ruslo/hunter,stohrendorf/hunter,shekharhimanshu/hunter,xsacha/hunter,madmongo1/hunter,dvirtz/hunter,ThomasFeher/hunter,isaachier/hunter,ledocc/hunter,ErniBrown/hunter,mchiasson/hunter,ruslo/hunter,designerror/hunter,akalsi87/hunter,tatraian/hunter,pretyman/hunter,fwinnen/hunter,ledocc/hunter,lucmichalski/hunter,fwinnen/hunter,headupinclouds/hunter,alamaison/hunter,x10mind/hunter,zhuhaow/hunter,dan-42/hunter,fire-hunter/hunter,sumedhghaisas/hunter,akalsi87/hunter,ruslo/hunter,shekharhimanshu/hunter,vdsrd/hunter,caseymcc/hunter,daminetreg/hunter,isaachier/hunter,ulricheck/hunter,xsacha/hunter,ErniBrown/hunter,jkhoogland/hunter,alamaison/hunter,madmongo1/hunter,ulricheck/hunter,ruslo/hunter,mchiasson/hunter,ingenue/hunter,ThomasFeher/hunter,fire-hunter/hunter,zhuhaow/hunter,sumedhghaisas/hunter,daminetreg/hunter,x10mind/hunter,xsacha/hunter,dmpriso/hunter,sumedhghaisas/hunter,alamaison/hunter,caseymcc/hunter,Knitschi/hunter,isaachier/hunter,designerror/hunter,RomanYudintsev/hunter,dan-42/hunter,ikliashchou/hunter,headupinclouds/hunter,Knitschi/hunter,ikliashchou/hunter