Fixing performance issue of checker validation.
Fixing performance issue of checker validation.

The validation process was passing most of its time in the construction of
the name of the current context.

8l/coq,SkySkimmer/coq,gares/coq,gmalecha/coq,amintimany/coq,ejgallego/coq,JasonGross/coq,amintimany/coq,letouzey/coq-wip,TheTypoMaster/coq,herbelin/github-coq,Ptival/coq,Zimmi48/coq,ale-f/coq,ppedrot/coq,Ptival/coq,coq/coq,gares/coq,jpdeplaix/coq,Matafou/coq,gmalecha/coq,coq/coq,aspiwack/coq,pirapira/coq2rust,maximedenes/coq,ejgallego/coq,ejgallego/coq,william-lawvere/coq,Lionel-Rieg/coq,herbelin/github-coq,SkySkimmer/coq,Lionel-Rieg/coq,silene/coq,8l/coq,TOSPIO/coq,ppedrot/coq,TOSPIO/coq,silene/coq,jpdeplaix/coq,gares/coq,gmalecha/coq,pirapira/coq2rust,Matafou/coq,maximedenes/coq,TheTypoMaster/coq,mattam82/coq,TheTypoMaster/coq,mattam82/coq,barras/coq,aspiwack/coq,ppedrot/coq,Matafou/coq,Zimmi48/coq,JasonGross/coq,mlasson/coq,Zimmi48/coq,coq/coq,mlasson/coq,ale-f/coq,JasonGross/coq,mlasson/coq,asr/coq,ejgallego/coq,letouzey/coq-wip,pirapira/coq2rust,william-lawvere/coq,letouzey/coq-wip,SkySkimmer/coq,mattam82/coq,JasonGross/coq,asr/coq,8l/coq,herbelin/github-coq,silene/coq,ppedrot/coq,william-lawvere/coq,aspiwack/coq,gares/coq,SkySkimmer/coq,coq/coq,ale-f/coq,ppedrot/coq,TOSPIO/coq,barras/coq,maximedenes/coq,Ptival/coq,letouzey/coq-wip,jpdeplaix/coq,maximedenes/coq,barras/coq,Zimmi48/coq,maximedenes/coq,amintimany/coq,letouzey/coq-wip,asr/coq,gares/coq,Lionel-Rieg/coq