clang compile failure on FreeBSD about sparsehash HOT 3 OPEN

Seems to work fine with gcc, but clang is definitely not happy.  Since this 
uses tr1 things, does this code need a C11 refresh or something?

I'm getting compile error on FreeBSD 10 release with clang 3.3 too ( have you 
solved the problem yet? ) :
./src/sparsehash/internal/sparsehashtable.h:161:8: note: candidate constructor 
(the implicit copy constructor) not viable: requires 1
      argument, but 3 were provided
struct sparse_hashtable_iterator {
       ^
In file included from src/hashtable_test.cc:63:
./src/hash_test_interface.h:88:15: error: type 'typename 
sparse_hash_map<basic_string<char>, basic_string<char>, Hasher, Hasher,
      Alloc<basic_string<char>, unsigned long, 18446744073709551615> >::iterator' (aka 'sparse_hashtable_iterator<std::__1::pair<const
      std::__1::basic_string<char>, std::__1::basic_string<char> >, std::__1::basic_string<char>, <anonymous>::Hasher,
      google::sparse_hash_map<std::__1::basic_string<char>, std::__1::basic_string<char>, <anonymous>::Hasher, <anonymous>::Hasher,
      <anonymous>::Alloc<std::__1::basic_string<char>, unsigned long, 18446744073709551615> >::SelectKey,
      google::sparse_hash_map<std::__1::basic_string<char>, std::__1::basic_string<char>, <anonymous>::Hasher, <anonymous>::Hasher,
      <anonymous>::Alloc<std::__1::basic_string<char>, unsigned long, 18446744073709551615> >::SetKey, <anonymous>::Hasher,
      <anonymous>::Alloc<std::__1::basic_string<char>, unsigned long, 18446744073709551615> >') is not a direct or virtual base of
      'google::BaseHashtableInterface<google::sparse_hash_map<std::__1::basic_string<char>, std::__1::basic_string<char>,
      <anonymous>::Hasher, <anonymous>::Hasher, <anonymous>::Alloc<std::__1::basic_string<char>, unsigned long, 18446744073709551615> >
      >::iterator'
        : HT::iterator(it), parent_(parent) { }
              ^~~~~~~~
./src/hash_test_interface.h:144:12: note: in instantiation of member function
      'google::BaseHashtableInterface<google::sparse_hash_map<std::__1::basic_string<char>, std::__1::basic_string<char>,
      <anonymous>::Hasher, <anonymous>::Hasher, <anonymous>::Alloc<std::__1::basic_string<char>, unsigned long, 18446744073709551615> >
      >::iterator::iterator' requested here
    return iterator(ht_.begin(), this);
           ^
src/hashtable_test.cc:620:25: note: in instantiation of member function
      'google::BaseHashtableInterface<google::sparse_hash_map<std::__1::basic_string<char>, std::__1::basic_string<char>,
      <anonymous>::Hasher, <anonymous>::Hasher, <anonymous>::Alloc<std::__1::basic_string<char>, unsigned long, 18446744073709551615> >
      >::begin' requested here
  EXPECT_TRUE(this->ht_.begin() == this->ht_.end());
                        ^
./src/testutil.h:51:9: note: expanded from macro 'EXPECT_TRUE'
  if (!(cond)) {                                        \
        ^
src/hashtable_test.cc:619:1: note: in instantiation of member function 
'<anonymous
      namespace>::TEST_onetype_HashtableAllTest_NormalIterators<google::HashtableInterface_SparseHashMap<std::__1::basic_string<char>,
      std::__1::basic_string<char>, <anonymous>::Hasher, <anonymous>::Hasher, <anonymous>::Alloc<std::__1::basic_string<char>, unsigned
      long, 18446744073709551615> > >::Run' requested here
TYPED_TEST(HashtableAllTest, NormalIterators) {
^
./src/testutil.h:171:7: note: expanded from macro 'TYPED_TEST'
      Run();                                                            \
      ^
src/hashtable_test.cc:619:1: note: in instantiation of member function 
'<anonymous
      namespace>::TEST_onetype_HashtableAllTest_NormalIterators<google::HashtableInterface_SparseHashMap<std::__1::basic_string<char>,
      std::__1::basic_string<char>, <anonymous>::Hasher, <anonymous>::Hasher, <anonymous>::Alloc<std::__1::basic_string<char>, unsigned
      long, 18446744073709551615> > >::TEST_onetype_HashtableAllTest_NormalIterators' requested here
TYPED_TEST(HashtableAllTest, NormalIterators) {
^
./src/testutil.h:205:68: note: expanded from macro 'TYPED_TEST'
        TEST_onetype_##superclass##_##testname<superclass##_type7> t;   \
                                                                   ^
fatal error: too many errors emitted, stopping now [-ferror-limit=]
3 warnings and 20 errors generated.
*** Error code 1

Seems clang is a bit more stringent - some of the allocators used in the test 
are wrong. Seems hashmap allocators need to return pairs. Separately looks like 
there's something wonky going on in libc++ or sparsehash itself - the first 
element of the pair needs to be const. Not sure why.

Either way - here's a patch to fix the compile with clang.