Add const to some member functions of SuccIterator.

The operator+() and operator-() do not change the member
variables of SuccIterator.  This CL will qualify the *this*
pointer with const.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@201933 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Support/CFG.h

@@ -208,7 +208,7 @@ class SuccIterator : public std::iterator<std::random_access_iterator_tag, BB_,
     return *this;
   }
 
-  inline Self operator+(int Right) {
+  inline Self operator+(int Right) const {
     Self tmp = *this;
     tmp += Right;
     return tmp;
@@ -218,11 +218,11 @@ class SuccIterator : public std::iterator<std::random_access_iterator_tag, BB_,
     return operator+=(-Right);
   }
 
-  inline Self operator-(int Right) {
+  inline Self operator-(int Right) const {
     return operator+(-Right);
   }
 
-  inline int operator-(const Self& x) {
+  inline int operator-(const Self& x) const {
     assert(Term == x.Term && "Cannot work on iterators of different blocks!");
     int distance = idx - x.idx;
     return distance;