Work around French babel's incompatibility with prettyref

In classic (pdf)latex, where the colon is activated, detokenize
the argument of \prettyref.

Fix proposed by egreg at
https://tex.stackexchange.com/a/527912/19291

lib/languages

@@ -498,6 +498,7 @@ Language canadien
 	BabelName        acadian
 	PolyglossiaName  french
 	PolyglossiaOpts  "variant=canadian"
+	ActiveChars      ;!?:
 	XindyName        french
 	QuoteStyle       french
 	Encoding         iso8859-15
@@ -705,6 +706,7 @@ Language french
 	GuiName          "French"
 	HasGuiSupport    true
 	BabelName        french
+	ActiveChars      ;!?:
 	PolyglossiaName  french
 	XindyName        french
 	QuoteStyle       french

src/LaTeXFeatures.cpp

@@ -1284,6 +1284,14 @@ string const LaTeXFeatures::getPackages() const
 	// The rest of these packages are somewhat more complicated
 	// than those above.
 
+	// Babel languages with activated colon (such as French) break
+	// with prettyref. Work around that.
+	if (!runparams_.isFullUnicode() && useBabel()
+	    && mustProvide("prettyref") && contains(getActiveChars(), ':')) {
+		packages << "% Make prettyref compatible with babel active colon\n"
+			 << "\\def\\prettyref#1{\\expandafter\\@prettyref\\detokenize{#1:}}\n";
+	}
+
 	if (mustProvide("changebar")) {
 		packages << "\\usepackage";
 		if (runparams_.flavor == Flavor::LaTeX