ebnf: add empty package, and ebnf grammar copied from wikipedia

Signed-off-by: Alejandro Mery <amery@geeks.cl>
ebnf:doc: add syntax file for vim

Signed-off-by: Alejandro Mery <amery@geeks.cl>
ebnf:doc: add final draft of iso 14977

Signed-off-by: Alejandro Mery <amery@geeks.cl>