ret-void: warn for implicit type
Currently, no warning is given for symbols for which no
type is explicitely given. But for functions we received
a pointless warning like here under if the returned type
is effectively an int:
warning: incorrect type in return expression (invalid types)
expected incomplete type
got int
Fix this by issuing the warning.
Also give an implicit type of int, as required by C89, to
avoid pointless warning about the expected incomplete type.
Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>