Rewrite grammar to implement operator precedence without using %right or %prec.

Rewrite grammar to implement operator precedence without using %right or %prec.

Arithmetic operator should now behave as expeted and tests can now be written
without superfluous parenthesis, for example:

syscall:select:entry
/($1 == 0) || (pid == $1)/
{
}

Can now be written:

syscall:select:entry
/$1 == 0 || pid == $1/
{
}

While here improve filter debugging support.