Factorize the parsing rules of [Record] and the other kind of type definitions.
Factorize the parsing rules of [Record] and the other kind of type definitions.

They were almost identical, except some unused misplaced coercion symbol in the non-[Record] rule.

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