Use HTTPS for submodules

.gitmodules

 [submodule "coqprime"]
 	path = coqprime
-	url = git@gl.mathhub.info:Coq/coqprime.git
+	url = https://gl.mathhub.info/Coq/coqprime.git
 [submodule "mathcomp-bigenough"]
 	path = mathcomp-bigenough
-	url = git@gl.mathhub.info:Coq/mathcomp-bigenough.git
+	url = https://gl.mathhub.info/Coq/mathcomp-bigenough.git
 [submodule "mathcomp-algebra"]
 	path = mathcomp-algebra
-	url = git@gl.mathhub.info:Coq/mathcomp-algebra.git
+	url = https://gl.mathhub.info/Coq/mathcomp-algebra.git
 [submodule "list-plus"]
 	path = list-plus
-	url = git@gl.mathhub.info:Coq/list-plus.git
+	url = https://gl.mathhub.info/Coq/list-plus.git
 [submodule "iterable"]
 	path = iterable
-	url = git@gl.mathhub.info:Coq/iterable.git
+	url = https://gl.mathhub.info/Coq/iterable.git
 [submodule "io-list"]
 	path = io-list
-	url = git@gl.mathhub.info:Coq/io-list.git
+	url = https://gl.mathhub.info/Coq/io-list.git
 [submodule "io"]
 	path = io
-	url = git@gl.mathhub.info:Coq/io.git
+	url = https://gl.mathhub.info/Coq/io.git
 [submodule "interval"]
 	path = interval
-	url = git@gl.mathhub.info:Coq/interval.git
+	url = https://gl.mathhub.info/Coq/interval.git
 [submodule "geometric-algebra"]
 	path = geometric-algebra
-	url = git@gl.mathhub.info:Coq/geometric-algebra.git
+	url = https://gl.mathhub.info/Coq/geometric-algebra.git
 [submodule "function-ninjas"]
 	path = function-ninjas
-	url = git@gl.mathhub.info:Coq/function-ninjas.git
+	url = https://gl.mathhub.info/Coq/function-ninjas.git
 [submodule "functional-algebra"]
 	path = functional-algebra
-	url = git@gl.mathhub.info:Coq/functional-algebra.git
+	url = https://gl.mathhub.info/Coq/functional-algebra.git
 [submodule "flocq"]
 	path = flocq
-	url = git@gl.mathhub.info:Coq/flocq.git
+	url = https://gl.mathhub.info/Coq/flocq.git
 [submodule "fcsl-pcm"]
 	path = fcsl-pcm
-	url = git@gl.mathhub.info:Coq/fcsl-pcm.git
+	url = https://gl.mathhub.info/Coq/fcsl-pcm.git
 [submodule "ext-lib"]
 	path = ext-lib
-	url = git@gl.mathhub.info:Coq/ext-lib.git
+	url = https://gl.mathhub.info/Coq/ext-lib.git
 [submodule "error-handlers"]
 	path = error-handlers
-	url = git@gl.mathhub.info:Coq/error-handlers.git
+	url = https://gl.mathhub.info/Coq/error-handlers.git
 [submodule "equations"]
 	path = equations
-	url = git@gl.mathhub.info:Coq/equations.git
+	url = https://gl.mathhub.info/Coq/equations.git
 [submodule "disel"]
 	path = disel
-	url = git@gl.mathhub.info:Coq/disel.git
+	url = https://gl.mathhub.info/Coq/disel.git
 [submodule "cunit"]
 	path = cunit
-	url = git@gl.mathhub.info:Coq/cunit.git
+	url = https://gl.mathhub.info/Coq/cunit.git
 [submodule "coquelicot"]
 	path = coquelicot
-	url = git@gl.mathhub.info:Coq/coquelicot.git
+	url = https://gl.mathhub.info/Coq/coquelicot.git
 [submodule "charge-core"]
 	path = charge-core
-	url = git@gl.mathhub.info:Coq/charge-core.git
+	url = https://gl.mathhub.info/Coq/charge-core.git
 [submodule "cfml"]
 	path = cfml
-	url = git@gl.mathhub.info:Coq/cfml.git
+	url = https://gl.mathhub.info/Coq/cfml.git
 [submodule "bignums"]
 	path = bignums
-	url = git@gl.mathhub.info:Coq/bignums.git
+	url = https://gl.mathhub.info/Coq/bignums.git
 [submodule "foundation"]
 	path = foundation
-	url = git@gl.mathhub.info:Coq/foundation.git
+	url = https://gl.mathhub.info/Coq/foundation.git