Add STL begin()/end() functions to List and IdList.

This will allow us to use it in the C++11 foreach loop, as well
as simplify use of STL <algorithms>.

src/dsc.h

@@ -195,6 +195,11 @@ public:
         return prev + 1;
     }
 
+    T *begin() { return &elem[0]; }
+    T *end() { return &elem[n]; }
+    const T *begin() const { return &elem[0]; }
+    const T *end() const { return &elem[n]; }
+
     void ClearTags() {
         int i;
         for(i = 0; i < n; i++) {
@@ -351,6 +356,11 @@ public:
         return prev + 1;
     }
 
+    T *begin() { return &elem[0]; }
+    T *end() { return &elem[n]; }
+    const T *begin() const { return &elem[0]; }
+    const T *end() const { return &elem[n]; }
+
     void ClearTags() {
         int i;
         for(i = 0; i < n; i++) {