scons: allow for boost lib symlinks without dashes, and search on libboost_thread if building with multi threading support (to accomodate potentially limited thread lib names on gentoo)
scons: allow for boost lib symlinks without dashes, and search on libboost_thread if building with multi threading support (to accomodate potentially limited thread lib names on gentoo)

rouault/mapnik,jwomeara/mapnik,zerebubuth/mapnik,mapycz/mapnik,lightmare/mapnik,kapouer/mapnik,naturalatlas/mapnik,stefanklug/mapnik,qianwenming/mapnik,cjmayo/mapnik,mapnik/python-mapnik,jwomeara/mapnik,kapouer/mapnik,mapnik/python-mapnik,yiqingj/work,davenquinn/python-mapnik,yohanboniface/python-mapnik,Mappy/mapnik,Mappy/mapnik,mapnik/mapnik,jwomeara/mapnik,strk/mapnik,cjmayo/mapnik,strk/mapnik,manz/python-mapnik,strk/mapnik,mapnik/mapnik,lightmare/mapnik,naturalatlas/mapnik,yiqingj/work,manz/python-mapnik,lightmare/mapnik,tomhughes/mapnik,yohanboniface/python-mapnik,mapnik/mapnik,lightmare/mapnik,whuaegeanse/mapnik,rouault/mapnik,mbrukman/mapnik,mapycz/mapnik,tomhughes/mapnik,kapouer/mapnik,Mappy/mapnik,yohanboniface/python-mapnik,stefanklug/mapnik,mbrukman/mapnik,cjmayo/mapnik,garnertb/python-mapnik,Mappy/mapnik,sebastic/python-mapnik,pnorman/mapnik,naturalatlas/mapnik,yiqingj/work,tomhughes/mapnik,mapycz/python-mapnik,jwomeara/mapnik,qianwenming/mapnik,whuaegeanse/mapnik,sebastic/python-mapnik,qianwenming/mapnik,davenquinn/python-mapnik,kapouer/mapnik,qianwenming/mapnik,Airphrame/mapnik,sebastic/python-mapnik,zerebubuth/mapnik,tomhughes/python-mapnik,rouault/mapnik,mapycz/python-mapnik,zerebubuth/mapnik,pramsey/mapnik,stefanklug/mapnik,davenquinn/python-mapnik,pramsey/mapnik,pnorman/mapnik,pramsey/mapnik,garnertb/python-mapnik,Uli1/mapnik,yiqingj/work,stefanklug/mapnik,strk/mapnik,pramsey/mapnik,mapnik/mapnik,naturalatlas/mapnik,mapycz/mapnik,Uli1/mapnik,Uli1/mapnik,tomhughes/python-mapnik,pnorman/mapnik,whuaegeanse/mapnik,pnorman/mapnik,CartoDB/mapnik,whuaegeanse/mapnik,mapnik/python-mapnik,mbrukman/mapnik,Airphrame/mapnik,cjmayo/mapnik,manz/python-mapnik,Airphrame/mapnik,Airphrame/mapnik,garnertb/python-mapnik,tomhughes/mapnik,CartoDB/mapnik,rouault/mapnik,qianwenming/mapnik,mbrukman/mapnik,Uli1/mapnik,CartoDB/mapnik,tomhughes/python-mapnik