Normalize address-bar schemes and host:port inputs before URL validation #546

The address normalizer preserves any input matching the scheme regex, but its allow check accepts only lowercase http:// and https://. Uppercase-scheme URLs such as HTTPS://example.org are silently rejected, and common non-loopback host:port values such as example.org:8080 are mistaken for a scheme and discarded. Canonicalize allowed scheme casing and distinguish a host/port from an arbitrary URI scheme before validation.