[Polly][Refactor] Change the comment style to silence -Wcomment

[jdoerfert]

Summary

-Wcomment complained about a "multi-line comment" caused by the
 ascii art used in ScopHelper to describe the CFG.

[jdoerfert]

Closed by commit rL219207 (authored by @jdoerfert).

lib/Support/ScopHelper.cpp

if (!EnteringBB) {
     EnteringBB = OldEntry;
   }
 
   // Create an unconditional entry edge.
   if (EnteringBB->getTerminator()->getNumSuccessors() != 1) {
     BasicBlock *EntryBB = NewEntry ? NewEntry : OldEntry;
     BasicBlock *SplitEdgeBB = SplitEdge(EnteringBB, EntryBB, P);
 
-    // Once the edge between EnteringBB and EntryBB is split, two cases arise.
-    // The first is simple. The new block is inserted between EnteringBB and
-    // EntryBB. In this case no further action is needed. However it might
-    // happen (if the splitted edge is not critical) that the new block is
-    // inserted __after__ EntryBB causing the following situation:
-    //
-    // EnteringBB
-    //     |
-    //    / \
-    //    |  \-> some_other_BB_not_in_R
-    //    V
-    // EntryBB
-    //    |
-    //    V
-    // SplitEdgeBB
-    //
-    // In this case we need to swap the role of EntryBB and SplitEdgeBB.
+    /***************************************************************************
+      Once the edge between EnteringBB and EntryBB is split, two cases arise.
+      The first is simple. The new block is inserted between EnteringBB and
+      EntryBB. In this case no further action is needed. However it might
+      happen (if the splitted edge is not critical) that the new block is
+      inserted __after__ EntryBB causing the following situation:
+
+      EnteringBB
+          |
+         / \
+         |  \-> some_other_BB_not_in_R
+         V
+      EntryBB
+         |
+         V
+      SplitEdgeBB
+
+      In this case we need to swap the role of EntryBB and SplitEdgeBB.
+    ***************************************************************************/
 
     // Check which case SplitEdge produced:
     if (SplitEdgeBB->getTerminator()->getSuccessor(0) == EntryBB) {
       // First (simple) case.
       EnteringBB = SplitEdgeBB;
     } else {
       // Second (complicated) case.
       NewEntry = SplitEdgeBB;