One pass over GlobOpt.cpp, moving and consting

I moved a good number of functions to GlobOptBlockData and BasicBlock.
There's also some additions that should make working with const opnds
and syms more successful.

Author: Penguinwizzard

lib/Backend/FlowGraph.cpp

@@ -302,11 +302,11 @@ class BasicBlock
 
     BasicBlock * GetNext()
     {
-        BasicBlock *block = this;
+        BasicBlock *block = this->next;
 
-        do {
+        while (block && block->isDeleted) {
             block = block->next;
-        } while (block && block->isDeleted);
+        }
 
         return block;
     }
@@ -737,7 +737,7 @@ class Loop
     void                SetImplicitCallFlags(Js::ImplicitCallFlags flags);
     Js::LoopFlags GetLoopFlags() const { return loopFlags; }
     void SetLoopFlags(Js::LoopFlags val) { loopFlags = val; }
-    bool                CanHoistInvariants();
+    bool                CanHoistInvariants() const;
     bool                CanDoFieldCopyProp();
     bool                CanDoFieldHoist();
     void                SetHasCall();

lib/Backend/FlowGraph.h

@@ -27,8 +27,8 @@ class HashBucket
 class Key
 {
 public:
-    static uint Get(Sym *sym) { return static_cast<uint>(sym->m_id); }
-    static uint Get(ExprHash hash) { return static_cast<uint>(hash); }
+    static uint Get(Sym const *sym) { return static_cast<uint>(sym->m_id); }
+    static uint Get(ExprHash hash)  { return static_cast<uint>(hash); }
 };
 
 #define FOREACH_GLOBHASHTABLE_ENTRY(bucket, hashTable) \