Add a few output files to .gitignore.
Add a few output files to .gitignore.

chemhack/benchmark,nickhutchinson/benchmark,nickhutchinson/benchmark-cxx03,chandlerc/benchmark,Photonomie/benchmark,Photonomie/benchmark,gezidan/benchmark,subailong/benchmark,google/benchmark,efcs/benchmark,xlqian/benchmark,disconnect3d/benchmark,chemhack/benchmark,fuchsia-mirror/third_party-benchmark,quantumsteve/benchmark,everbase/benchmark,eliben/benchmark,LepelTsmok/benchmark,LepelTsmok/benchmark,codygray/benchmark,chandlerc/benchmark,Photonomie/benchmark,fuchsia-mirror/third_party-benchmark,quantumsteve/benchmark,quantumsteve/benchmark,nickhutchinson/benchmark,codygray/benchmark,ntx-/benchmark,chandlerc/benchmark,fuchsia-mirror/third_party-benchmark,subailong/benchmark,quantumsteve/benchmark,gezidan/benchmark,Photonomie/benchmark,nickhutchinson/benchmark-cxx03,bowlofstew/benchmark,eliben/benchmark,ntx-/benchmark,disconnect3d/benchmark,chemhack/benchmark,eliben/benchmark,disconnect3d/benchmark,bowlofstew/benchmark,mockingbirdnest/benchmark,mockingbirdnest/benchmark,ntx-/benchmark,gezidan/benchmark,disconnect3d/benchmark,nickhutchinson/benchmark-cxx03,nickhutchinson/benchmark,chandlerc/benchmark,everbase/benchmark,bowlofstew/benchmark,google/benchmark,efcs/benchmark,google/benchmark,subailong/benchmark,mockingbirdnest/benchmark,eliben/benchmark,codygray/benchmark,xlqian/benchmark,fuchsia-mirror/third_party-benchmark,codygray/benchmark,everbase/benchmark,efcs/benchmark,subailong/benchmark,LepelTsmok/benchmark,LepelTsmok/benchmark,bowlofstew/benchmark,ntx-/benchmark,gezidan/benchmark,chemhack/benchmark,xlqian/benchmark,nickhutchinson/benchmark-cxx03,xlqian/benchmark,mockingbirdnest/benchmark,everbase/benchmark,efcs/benchmark,nickhutchinson/benchmark