Support /ipfs/ absolute paths for gateway when Host header is set

#### Type:
Feature

#### Description:

Today, when making a request to the HTTP gateway with `Host` header set, it does dnslink lookup and serves the content at that hash. This is great for hosting a website directly off IPFS. However, when I want to put links in my website to other content on IPFS, I want to use the correct `href="/ipfs/hash"` style. When viewing content on a gateway this works, when viewing content with the IPFS-companion this works, but for a "normal" browser using my domain with Host header request to the gateway it results in an error (no link named ipfs)

Please allow /ipfs absolute paths to be resolved even when Host header is used.