Fix compile warnings when debug is disabled
Fix compile warnings when debug is disabled

Initialize the 'res' pointer to NULL.

Borrow the 'errno' variable rather than using an 'err' variable local
to graphene_aligned_alloc. There is some precedent for this, as the
existing code also set 'errno = 0' before calling the corresponding
alloc routine.

ebassi/graphene,ebassi/graphene