Support custom deleter for SrsUniquePtr.

[winlinvip]

SrsUniquePtr does not support array or object created by malloc, because we only use delete to dispose the resource. You can use a custom function to free the memory allocated by malloc or other allocators.

     char* p = (char*)malloc(1024);
      SrsUniquePtr<char> ptr(p, your_free_chars);

This is used to replace the SrsAutoFreeH. For example:

      addrinfo* r = NULL;
      SrsAutoFreeH(addrinfo, r, freeaddrinfo);
      getaddrinfo("127.0.0.1", NULL, &hints, &r);

Now, this can be replaced by:

      addrinfo* r = NULL;
      getaddrinfo("127.0.0.1", NULL, &hints, &r);
      SrsUniquePtr<addrinfo> r2(r, freeaddrinfo);

Please aware that there is a slight difference between SrsAutoFreeH and SrsUniquePtr. SrsAutoFreeH will track the address of pointer, while SrsUniquePtr will not.

      addrinfo* r = NULL;
      SrsAutoFreeH(addrinfo, r, freeaddrinfo); // r will be freed even r is changed later.
      SrsUniquePtr<addrinfo> ptr(r, freeaddrinfo); // crash because r is an invalid pointer.