[eacsl] Update copyright year to 2021

...rvation_model/segment_model/e_acsl_segment_omodel_debug.c

..._model/segment_model/e_acsl_segment_timestamp_retrieval.c

...observation_model/segment_model/e_acsl_segment_tracking.c

...observation_model/segment_model/e_acsl_segment_tracking.h

...sl/observation_model/segment_model/e_acsl_shadow_layout.c

...sl/observation_model/segment_model/e_acsl_shadow_layout.h

src/plugins/e-acsl/src/analyses/bound_variables.ml

src/plugins/e-acsl/src/analyses/bound_variables.mli

src/plugins/e-acsl/src/analyses/e_acsl_visitor.ml

src/plugins/e-acsl/src/analyses/e_acsl_visitor.mli

src/plugins/e-acsl/src/analyses/exit_points.ml

src/plugins/e-acsl/src/analyses/exit_points.mli

src/plugins/e-acsl/src/analyses/interval.ml

src/plugins/e-acsl/src/analyses/interval.mli

src/plugins/e-acsl/src/analyses/literal_strings.ml

src/plugins/e-acsl/src/analyses/literal_strings.mli

src/plugins/e-acsl/src/analyses/logic_normalizer.ml

src/plugins/e-acsl/src/analyses/logic_normalizer.mli

src/plugins/e-acsl/src/analyses/lscope.ml

src/plugins/e-acsl/src/analyses/lscope.mli