Drop iostream from solver.cc
Drop iostream from solver.cc

Change-Id: I512a247c183113ef5dcf09e13f19c17c83293f21

stonier/ceres_solver,stonier/ceres_solver,timfel/ceres-bin,ysonggit/ceres-solver,whuaegeanse/ceres-solver,entylop/ceres-solver,DougFirErickson/ceres-solver,kartikkumar/ceres-solver,ysonggit/ceres-solver,timfel/ceres-bin,entylop/ceres-solver,stonier/ceres_solver,timfel/ceres-bin,whuaegeanse/ceres-solver,whuaegeanse/ceres-solver,kartikkumar/ceres-solver,entylop/ceres-solver,entylop/ceres-solver,whuaegeanse/ceres-solver,timfel/ceres-bin,DougFirErickson/ceres-solver,ysonggit/ceres-solver,ysonggit/ceres-solver,kartikkumar/ceres-solver,DougFirErickson/ceres-solver,kartikkumar/ceres-solver,DougFirErickson/ceres-solver,stonier/ceres_solver