Modify library/socket/socket/gethostbyname specs.

For specs "Socket#gethostbyname returns broadcast address info for
'<broadcast>'" and "Socket#gethostbyname returns broadcast address
info for '<any>'", only the first item (address) of returned array
is tested.

Later, some specs shall be added to verify that latest item of returned array contains
address as a packed string.
Modify Socket::Foreign.getaddrinfo to handle special host strings.

Modify Socket::Foreign.getaddrinfo to handle special host strings
'<any>' and '<broadcast>'.

Modification made for 1.8, 1.9 and 2.0 versions.