Command.declare_definition: grab the fix_exn early (follows 77cf18e)
Command.declare_definition: grab the fix_exn early (follows 77cf18e)

When a future is fully forced (joined), the fix_exn is dropped,
since joined futures are values (hence they cannot raise exceptions).

When a future for a transparent definition enters the environment
it is joined.  If one needs to pick its fix_exn, he should do it
before that.

william-lawvere/coq,maximedenes/coq,SkySkimmer/coq,maximedenes/coq,coq/coq,mattam82/coq,ejgallego/coq,JasonGross/coq,Matafou/coq,ppedrot/coq,SkySkimmer/coq,gares/coq,william-lawvere/coq,Zimmi48/coq,silene/coq,Zimmi48/coq,mattam82/coq,SkySkimmer/coq,JasonGross/coq,jpdeplaix/coq,letouzey/coq-wip,silene/coq,maximedenes/coq,Lionel-Rieg/coq,JasonGross/coq,letouzey/coq-wip,jpdeplaix/coq,ejgallego/coq,ejgallego/coq,ppedrot/coq,gares/coq,Lionel-Rieg/coq,mattam82/coq,ppedrot/coq,amintimany/coq,gares/coq,Zimmi48/coq,letouzey/coq-wip,jpdeplaix/coq,Zimmi48/coq,gares/coq,william-lawvere/coq,Lionel-Rieg/coq,herbelin/github-coq,ejgallego/coq,amintimany/coq,Ptival/coq,herbelin/github-coq,coq/coq,amintimany/coq,SkySkimmer/coq,silene/coq,Ptival/coq,coq/coq,Matafou/coq,gares/coq,ppedrot/coq,letouzey/coq-wip,Matafou/coq,Ptival/coq,letouzey/coq-wip,herbelin/github-coq,ppedrot/coq,coq/coq,JasonGross/coq,maximedenes/coq,maximedenes/coq