Completion of error handling

[elfring]

Would you like to add more error handling for return values from functions like the following?

• malloc ⇒ intsetNew
• printf ⇒ ziplistRepr
• sigaction ⇒ Server::MainLoop

[loveyacper]

#4
These code is from redis.

[elfring]

I suggest to avoid ignorance of return values a bit more.
Would you like to detect every error situation as early as possible?