Ensure that the docs examples verify as Cretonne IL.

Any *.cton files in the docs directory are now included when running the
test-all.sh script. This is to ensure that the examples are in fact
correct IL.

Always print NaN and Inf floats with a sign. Print the positive ones as
+NaN and +Inf to make them easier to parse.

test-all.sh

@@ -79,6 +79,6 @@ export CTONUTIL="$topdir/target/release/cton-util"
 
 cd "$topdir"
 banner "File tests"
-"$CTONUTIL" test filetests
+"$CTONUTIL" test filetests docs
 
 banner "OK"