Adding an option Loose Hint Behavior to handle hints loaded but not imported.
Adding an option Loose Hint Behavior to handle hints loaded but not imported.

It accepts three distinct flags:
- "Lax", which is the default one, sets the old behaviour, i.e. a non-imported
hint behaves the same as an imported one.
- "Warn" outputs a warning when a non-imported hint is used. Note that this is
an over-approximation, because a hint may be triggered by an eauto run that
will eventually fail and backtrack.
- "Strict" changes the behaviour of an unloaded hint to the one of the fail
tactic, allowing to emulate the hopefully future import-scoped hint mechanism.

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