Global replace of u_int??_t with C9x standard based uintxx_t
in order to remove some tricky and overlapping portability logic
from acinclude.m4 and leave it in only m4/stdint.m4.
to copy it over and over again. Changed header inclusion order in backend
files to include backend.h after sanei_backend.h. Based on a patch from stef
<stef-listes@wanadoo.fr>.