SPF prefix should be case insensitive

[bayerhonza]

RFC 7208 notes that literal text strings in ABNF are case-insensitive.

This means that following SPF records are valid but do not apear as valid records while using zdns with SPF module:

SPF record	zdns result
v=spf1	NOERROR
V=sPf1	NORECORD
v=SPF1	NORECORD

Checking the SPF prefix ("v=spf1") should be case-insensitive in order to conform to RFC.

[zakird]

Thanks! Would you be willing to submit a PR to address this?

[bayerhonza]

Yes, I will submit a PR together with #252

[zakird]

Fantastic, thank you!!