Avoid implementation defined types, e.g. unsigned

There are some cases where "int" or "unsigend" actually makes sense, but
in a large number of cases it is really supposed to be either a 32-bit
integer, or, in some cases, at least a 32-bit integer.  It is much to be
preferred to be clear about this.

Another reason is that at least some embedded platforms define, e.g.,
int32_t as "long" instead of "int".  For the ones I am aware of the
"int" and "long" are actually the same 32-bit integer, but that
distinction can cause trouble with printf format specifications.  So
again a good reason to be consistent in avoiding the
implementation-defined ones.

Signed-off-by: Erik Boasson <eb@ilities.com>

src/ddsrt/src/fibheap.c

@@ -207,7 +207,7 @@ void *ddsrt_fibheap_extract_min (const ddsrt_fibheap_def_t *fhdef, ddsrt_fibheap
        keys anyway to find the minimum */
     {
         ddsrt_fibheap_node_t *mark, *cursor, *newmin;
-        unsigned i;
+        uint32_t i;
         for (i = 0; roots[i] == NULL; i++) {
             assert (i+1 < min_degree_noninit);
         }