test.h: Don't force tests to use must_alloc

src/test.h

@@ -127,7 +127,7 @@ test_main(int argc, const char **argv, struct testdef tests[])
     return allok ? 0 : 1;
 }
 
-static void *
+void *
 must_alloc(testctx t, size_t size)
 {
     void *out = malloc(size);