Fix timedelta scalar multiplication

This fixes a bug in elementwiseScalarMultiplyTimeDelta introduced in !5 (merged): in the original implementation, we had something like scaled_td += lambda * base_td but f3844207 replaced it with something like scaled_td = lambda * base_td.

The bug was the reason why we urgently had to introduce d7586b2b into the master right before the first open-source release of ICON (several Buildbot tests on the DWD machine kept failing). That commit was dropped and the master was updated with force-push.

src/mtime_timedelta.c

@@ -1691,19 +1691,21 @@ elementwiseScalarMultiplyTimeDelta(struct _timedelta* base_td, int64_t lambda, s
       lambda = (int64_t)(llabs(lambda));
 
       /* Multiply each element by scalar. */
-      int64_t ms_temp = lambda * base_td->ms;
+      int64_t ms_temp = scaled_td->ms + lambda * base_td->ms;
       scaled_td->ms = (int)(ms_temp % NO_OF_MS_IN_A_SECOND);
-      int64_t s_temp = lambda*base_td->second + ms_temp / NO_OF_MS_IN_A_SECOND;
+
+      int64_t s_temp = scaled_td->second + lambda * base_td->second
+                       + ms_temp / NO_OF_MS_IN_A_SECOND;
       scaled_td->second = (int)(s_temp % 60);
 
-      int64_t m_temp = lambda*base_td->minute + s_temp / 60;
+      int64_t m_temp = scaled_td->minute + lambda * base_td->minute
+                       + s_temp / 60;
       scaled_td->minute = (int)(m_temp % 60);
 
-      int64_t h_temp = lambda*base_td->hour + m_temp / 60;
-      scaled_td->hour = (int)(h_temp % NO_OF_HOURS_IN_A_DAY);
+      scaled_td->hour += (int)(lambda * base_td->hour + m_temp / 60);
 
       /* Scalar multiplication must not give a value in excess of 24 hours. */
-      if ( h_temp >= NO_OF_HOURS_IN_A_DAY )
+      if ( scaled_td->hour >= NO_OF_HOURS_IN_A_DAY )
         {
           /* ERROR: Return on NULL. */
           return NULL;