Mod_subst.force: avoid using join when only one subst
Mod_subst.force: avoid using join when only one subst

git-svn-id: 44dc50bdcc0f5d1a212c497508dc9452e0b35e2b@16381 85f007b7-540e-0410-9357-904b9bb8a0f7

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