As stated by http://www.gnu.org/software/automake/manual/html_node/Yacc-and-Lex.html
"You should never explicitly mention the intermediate (C or C++) file in any SOURCES variable; only list the source file."
otherwise, the yacc and lex grammar are never regenerated.

Signed-off-by: zosrothko <zosrothko@orange.fr>