Can simplify InternedStringPool

now that the strings get interned anyway.  if we want to continue
down that road of interning BoxedStrings, we could probably do
away with InternedString's entirely.

src/core/stringpool.cpp

@@ -19,19 +19,8 @@
 namespace pyston {
 
 InternedString InternedStringPool::get(llvm::StringRef arg) {
-    auto it = interned.find(arg);
-
-    BoxedString* s;
-    if (it != interned.end()) {
-        s = it->second;
-    } else {
-        // HACK: should properly track this liveness:
-        s = internStringImmortal(arg);
-
-        // Note: make sure the key points to the value we just created, not the
-        // argument string:
-        interned[s->s()] = s;
-    }
+    // HACK: should properly track this liveness:
+    BoxedString* s = internStringImmortal(arg);
 
 #ifndef NDEBUG
     return InternedString(s, this);

src/core/stringpool.h

@@ -89,12 +89,6 @@ public:
 };
 
 class InternedStringPool {
-private:
-    // We probably don't need to pull in llvm::StringRef as the key, but it's better than std::string
-    // which I assume forces extra allocations.
-    // (We could define a custom string-pointer container but is it worth it?)
-    std::unordered_map<llvm::StringRef, BoxedString*> interned;
-
 public:
     void gcHandler(gc::GCVisitor* v);
     InternedString get(llvm::StringRef s);