vCard v3.0/v4.0 parsing: Bare BASE64 parameter is incorrectly recognized as ENCODING=BASE64

[respiranto]

When parsing a v3.0 or v4.0 vCard, a bare BASE64 parameter is wrongly parsed as if it was ENCODING=BASE64 (which would be valid for v2.1).

For v3.0, validate() yields the error that ENCODING=BASE64 is not valid, and with the REPAIR flag it translates that to ENCODING=B.
For v4.0, validate() yields the error that ENCODING is not a valid parameter.

I would expect that either

• parsing fails, or
• validate() yields the error message that BASE64 is not a valid parameter, or that bare parameter values are not supported in v3.0/v4.0.

Optionally, validate() with the REPAIR flag might do some suitable repairing.

See also #688.

[respiranto]

The problem seems to be that Parameter::guessParameterNameByValue() is applied not only to v2.1 vCards.