Add makefile for daytime
Add .gitignore

Ignored files are ...
* *.o
* daytime
Use standard c99
`daytime` works well
Handle errors in `fdopen`

Add error handling function `safe_fdopen`
Handle errors in `inet_pton`

Add error handling function `safe_inet_pton`
Retrun value of `inet_pton` means ...
* success when 1
* `src` is invalid network address when 0
* `af` does not contain a valid address family when -1
Handle errors in `socket`

Add error handling function `safe_socket`
Change pointer definition style

char * str ->
char *str
     ^^