记录一下 __gnu_cxx::hash_map传一个新allocator的写法

hash_map(size_type __n, const hasher& __hf,
const key_equal& __eql, const allocator_type& __a = allocator_type())

// 全局的角色指针Allocator
__gnu_cxx::__pool_alloc<Role*> g_rolePtrAlloc;

typedef __gnu_cxx::hash_map<
uint32_t,
Role*,
__gnu_cxx::hash<uint32_t>,
std::equal_to<uint32_t>,
__gnu_cxx::__pool_alloc<Role*> > Roles;
Roles roles(5000, __gnu_cxx::hash<uint32_t>(),
std::equal_to<uint32_t>(), g_rolePtrAlloc);