Return the host part of an evhttp_uri, or NULL if it has no host set.
The host may either be a regular hostname (conforming to the RFC 3986
"regname" production), or an IPv4 address, or the empty string, or a
bracketed IPv6 address, or a bracketed 'IP-Future' address.
Note that having a NULL host means that the URI has no authority
section, but having an empty-string host means that the URI has an
authority section with no host part. For example,
"mailto:user@example.com" has a host of NULL, but "file:///etc/motd"
has a host of "".
Return the host part of an evhttp_uri, or NULL if it has no host set. The host may either be a regular hostname (conforming to the RFC 3986 "regname" production), or an IPv4 address, or the empty string, or a bracketed IPv6 address, or a bracketed 'IP-Future' address.
Note that having a NULL host means that the URI has no authority section, but having an empty-string host means that the URI has an authority section with no host part. For example, "mailto:user@example.com" has a host of NULL, but "file:///etc/motd" has a host of "".