RFC 3986 section 3.1 defines URI schemes as case-insensitive (though
the canonical form is always lowercase).
Use strcasecmp() rather than strcmp() to allow for case insensitivity
in URI schemes.
Requested-by: Andreas Hammarskjöld <junior@2PintSoftware.com>
Signed-off-by: Michael Brown <mcb30@ipxe.org>