Cerb magic end position is off-by-one

[dc-mak]

It includes the "@" or "$".

[dc-mak]

Specifically, lexbuf.lex_start_p is one-past.

cerberus/parsers/c/c_lexer.mll

Lines 504 to 514 in 73b0949

	and initial flags = parse
	(* Magic comments *)
	| "/*@" { let curr_p = lexbuf.lex_curr_p in
	let xs = magic flags lexbuf.lex_start_p lexbuf in
	match magic_token flags curr_p lexbuf.lex_start_p ('@' :: xs) with
	| Some tok -> tok
	| None -> initial flags lexbuf
	}
	(* Alternative magic comments *)
	| "/*$" { let curr_p = lexbuf.lex_curr_p in
	let xs = magic flags lexbuf.lex_start_p lexbuf in