Add missing keyword 'enum', to make compilation as C work again

low/heaps.c

@@ -317,7 +317,7 @@ void NS_PREFIX DisposeHeap (HEAP *theHeap)
  */
 /****************************************************************************/
 
-void *NS_PREFIX GetMem (HEAP *theHeap, MEM n, HeapAllocMode mode)
+void *NS_PREFIX GetMem (HEAP *theHeap, MEM n, enum HeapAllocMode mode)
 {
 #if UG_USE_SYSTEM_HEAP
   return malloc(n);
@@ -422,7 +422,7 @@ void *NS_PREFIX GetMem (HEAP *theHeap, MEM n, HeapAllocMode mode)
 #endif
 }
 
-void *NS_PREFIX GetMemUsingKey (HEAP *theHeap, MEM n, HeapAllocMode mode, INT key)
+void *NS_PREFIX GetMemUsingKey (HEAP *theHeap, MEM n, enum HeapAllocMode mode, INT key)
 {
   if (theHeap->type==SIMPLE_HEAP)
   {

low/heaps.h

@@ -213,8 +213,8 @@ INT          InitHeaps                (void);
 /* @{ */
 HEAP        *NewHeap                (enum HeapType type, MEM size, void *buffer);
 void         DisposeHeap            (HEAP *theHeap);
-void        *GetMem                 (HEAP *theHeap, MEM n, HeapAllocMode mode);
-void            *GetMemUsingKey                 (HEAP *theHeap, MEM n, HeapAllocMode mode, INT key);
+void        *GetMem                 (HEAP *theHeap, MEM n, enum HeapAllocMode mode);
+void            *GetMemUsingKey                 (HEAP *theHeap, MEM n, enum HeapAllocMode mode, INT key);
 void         DisposeMem             (HEAP *theHeap, void *buffer);
 
 void        *GetFreelistMemory      (HEAP *theHeap, INT size);