Test ServeMux's case folding
Test ServeMux's case folding

Psiphon-Inc/dns,ym/go-dns,AlexCheong/dns,modulexcite/dns,michaelharo/dns,asergeyev/dns,bragr/dns,skynet/dns,ezoic/dns,jmhodges/dns,hugozhu/dns,skyportsystems/dns,FiloSottile/dns,Git-Host/dns,curtiszimmerman/dns,benbearchen/dns,letsencrypt/dns,tsenart/dns,flebarbe/dns,cloudflare/dns,miekg/dns,jdef/dns,josephyzhou/dns,rolandshoemaker/dns,janstk/dns,ErikDubbelboer/dns,bboreham/dns,tempbottle/dns