fix bug #1717 about instrumentation of labeled stmt

src/plugins/e-acsl/doc/Changelog

src/plugins/e-acsl/env.ml

src/plugins/e-acsl/env.mli

src/plugins/e-acsl/label.ml

src/plugins/e-acsl/label.mli

src/plugins/e-acsl/main.ml

src/plugins/e-acsl/tests/e-acsl-runtime/bts1717.i

...s/e-acsl/tests/e-acsl-runtime/oracle/bts1717.1.err.oracle

...s/e-acsl/tests/e-acsl-runtime/oracle/bts1717.1.res.oracle

...ins/e-acsl/tests/e-acsl-runtime/oracle/bts1717.err.oracle

...ins/e-acsl/tests/e-acsl-runtime/oracle/bts1717.res.oracle

src/plugins/e-acsl/tests/e-acsl-runtime/oracle/gen_at.c

src/plugins/e-acsl/tests/e-acsl-runtime/oracle/gen_at2.c

src/plugins/e-acsl/tests/e-acsl-runtime/oracle/gen_bts1717.c

...plugins/e-acsl/tests/e-acsl-runtime/oracle/gen_bts17172.c

src/plugins/e-acsl/visit.ml