gfse: some correctness checks for concrete syntax

The editor now calls the GF server to check the syntax of expressions that
are part of concrete syntax (except for parameter types).
This is currently done by using the cc command of the GF shell, which puts
some unnecessary restricitons on operation definitions...

src/editor/simple/upload.cgi

@@ -219,6 +219,13 @@ case "$REQUEST_METHOD" in
                 *) error400
 	     esac
 	     ;;
+	cc=*)
+	     # Just to check an expression for syntax errors
+	     exp=$(qparse "$QUERY_STRING" cc)
+	     ContentType="text/plain; charset=$charset"
+	     cgiheaders
+	     echo "cc $exp" | GF_RESTRICTED=True gf -run
+	     ;;
         *) error400
     esac
 esac