move pool docs down under "more details"
move pool docs down under "more details"

The earlier section is a tutorial-style overview.  The latter section
is for side features like phony rules and header dependencies.  Pools
fit in with the latter.

atetubou/ninja,autopulated/ninja,ThiagoGarciaAlves/ninja,fifoforlifo/ninja,synaptek/ninja,nicolasdespres/ninja,colincross/ninja,drbo/ninja,mohamed/ninja,lizh06/ninja,hnney/ninja,mydongistiny/ninja,liukd/ninja,purcell/ninja,atetubou/ninja,atetubou/ninja,sxlin/dist_ninja,Qix-/ninja,ilor/ninja,nicolasdespres/ninja,ndsol/subninja,lizh06/ninja,synaptek/ninja,guiquanz/ninja,vvvrrooomm/ninja,nickhutchinson/ninja,AoD314/ninja,dpwright/ninja,ilor/ninja,automeka/ninja,TheOneRing/ninja,Qix-/ninja,nicolasdespres/ninja,synaptek/ninja,automeka/ninja,pathscale/ninja,tfarina/ninja,yannicklm/ninja,maruel/ninja,ThiagoGarciaAlves/ninja,fifoforlifo/ninja,Ju2ender/ninja,Ju2ender/ninja,jendrikillner/ninja,autopulated/ninja,jendrikillner/ninja,jimon/ninja,ninja-build/ninja,sgraham/ninja,bmeurer/ninja,nafest/ninja,syntheticpp/ninja,drbo/ninja,maruel/ninja,rjogrady/ninja,ctiller/ninja,jhanssen/ninja,mdempsky/ninja,AoD314/ninja,drbo/ninja,fifoforlifo/ninja,glensc/ninja,rnk/ninja,metti/ninja,jhanssen/ninja,juntalis/ninja,moroten/ninja,hnney/ninja,mgaunard/ninja,metti/ninja,maruel/ninja,glensc/ninja,juntalis/ninja,dendy/ninja,purcell/ninja,jhanssen/ninja,autopulated/ninja,Ju2ender/ninja,autopulated/ninja,colincross/ninja,dorgonman/ninja,syntheticpp/ninja,sorbits/ninja,ThiagoGarciaAlves/ninja,TheOneRing/ninja,mohamed/ninja,sxlin/dist_ninja,mgaunard/ninja,nickhutchinson/ninja,ctiller/ninja,hnney/ninja,moroten/ninja,juntalis/ninja,jimon/ninja,yannicklm/ninja,dendy/ninja,fuchsia-mirror/third_party-ninja,syntheticpp/ninja,yannicklm/ninja,synaptek/ninja,martine/ninja,nocnokneo/ninja,ignatenkobrain/ninja,sgraham/ninja,nico/ninja,mydongistiny/ninja,martine/ninja,dendy/ninja,AoD314/ninja,jendrikillner/ninja,dpwright/ninja,pathscale/ninja,vvvrrooomm/ninja,TheOneRing/ninja,tfarina/ninja,nickhutchinson/ninja,mydongistiny/ninja,nafest/ninja,tfarina/ninja,iwadon/ninja,mydongistiny/ninja,Maratyszcza/ninja-pypi,bradking/ninja,purcell/ninja,dorgonman/ninja,guiquanz/ninja,rjogrady/ninja,jimon/ninja,fuchsia-mirror/third_party-ninja,Maratyszcza/ninja-pypi,maruel/ninja,purcell/ninja,yannicklm/ninja,AoD314/ninja,tfarina/ninja,ThiagoGarciaAlves/ninja,dpwright/ninja,hnney/ninja,Ju2ender/ninja,mohamed/ninja,mdempsky/ninja,colincross/ninja,bmeurer/ninja,nafest/ninja,liukd/ninja,kissthink/ninja,sorbits/ninja,ninja-build/ninja,ignatenkobrain/ninja,sorbits/ninja,drbo/ninja,dendy/ninja,mohamed/ninja,dpwright/ninja,bradking/ninja,sxlin/dist_ninja,juntalis/ninja,lizh06/ninja,iwadon/ninja,nickhutchinson/ninja,nocnokneo/ninja,rjogrady/ninja,sxlin/dist_ninja,sxlin/dist_ninja,bmeurer/ninja,metti/ninja,jimon/ninja,sgraham/ninja,metti/ninja,ninja-build/ninja,vvvrrooomm/ninja,mdempsky/ninja,kissthink/ninja,automeka/ninja,bradking/ninja,lizh06/ninja,syntheticpp/ninja,sxlin/dist_ninja,guiquanz/ninja,martine/ninja,ctiller/ninja,nafest/ninja,nico/ninja,liukd/ninja,rjogrady/ninja,iwadon/ninja,ilor/ninja,nicolasdespres/ninja,ninja-build/ninja,kissthink/ninja,moroten/ninja,automeka/ninja,nico/ninja,nico/ninja,atetubou/ninja,kimgr/ninja,pathscale/ninja,colincross/ninja,glensc/ninja,ndsol/subninja,jendrikillner/ninja,Maratyszcza/ninja-pypi,rnk/ninja,martine/ninja,TheOneRing/ninja,kissthink/ninja,fifoforlifo/ninja,jhanssen/ninja,ignatenkobrain/ninja,fuchsia-mirror/third_party-ninja,mgaunard/ninja,kimgr/ninja,mdempsky/ninja,fuchsia-mirror/third_party-ninja,Maratyszcza/ninja-pypi,kimgr/ninja,vvvrrooomm/ninja,bradking/ninja,nocnokneo/ninja,pathscale/ninja,rnk/ninja,dorgonman/ninja,Qix-/ninja,ctiller/ninja,bmeurer/ninja,sgraham/ninja,kimgr/ninja,ndsol/subninja,iwadon/ninja,moroten/ninja,ndsol/subninja,glensc/ninja,ilor/ninja,sxlin/dist_ninja,rnk/ninja,ignatenkobrain/ninja,Qix-/ninja,dorgonman/ninja,mgaunard/ninja,sorbits/ninja,nocnokneo/ninja,guiquanz/ninja,liukd/ninja