prepare parser running context in upper layer than each parser

In older parse.c and parser interface, the parser itself prepares
setjmp and trashBox. However, many parsers do the same.

This patch prepares experimental new interface; parse.c prepares both
setjmp and trashBox before calling actual parser. Both of the are
passed to the parser as arguments.

This new interface is applied to vhdl.c for evaluating its usefulness.

Signed-off-by: Masatake YAMATO <yamato@redhat.com>