[STAT] Implement STATReuse

No idea what is the difference between Reuse and Free (presumably when
makeotf was used as a library to avoid re-allocating dynamic arrays?).
Implement it anyway for completeness sake, though it does not seem to
make any practical difference.

c/makeotf/makeotf_lib/source/hotconv/STAT.c

@@ -261,22 +261,27 @@ void STATWrite(hotCtx g) {
 }
 
 void STATReuse(hotCtx g) {
-}
-
-void STATFree(hotCtx g) {
     STATCtx h = g->ctx.STAT;
     long i;
 
-    dnaFREE(h->designAxes);
-    dnaFREE(h->axisValues);
-
     for (i = 0; i < h->axisValues.cnt; i++) {
         AxisValueTable *av = &h->axisValues.array[i];
         if (av->format == 4) {
             MEM_FREE(g, av->format4.axisValues);
         }
     }
 
+    h->designAxes.cnt = 0;
+    h->axisValues.cnt = 0;
+    h->elidedFallbackNameID = 0;
+}
+
+void STATFree(hotCtx g) {
+    STATCtx h = g->ctx.STAT;
+
+    dnaFREE(h->designAxes);
+    dnaFREE(h->axisValues);
+
     MEM_FREE(g, g->ctx.STAT);
 }