[fitsbits] Blank strings in FITS keywords.

Here's a little FITS lawyer nit.

Section 5.2.1 of the FITS standards document
notes that

KEYWORD1= ''

is distinct from

KEYWORD1= ' '

However I am unclear as to whether either of these are
distinct from

KEYWORD1= ' '

(where there are at least 8 blanks between the quotes).

The first two examples clearly use the free format for
the headers, but the third example could be in the fixed format.
Since a fixed format line cannot have fewer than 8 characters
in a character string header value, a sequence of 8 blanks is the only
way to specify these strings in the format that that standard
recommends people use.

Since one is allowed to intermix free and fixed format
cards in the header there is no context that can tell you which format the
card is in.

So it looks like

Example 1 EQV example 3
Example 2 EQV example 3
but
Example 1 NOT EQV example 2.

Is this true? If so I think this may be the only example
where this is the case and seems a little inelegant to me.
Probably too late to change
but it might have been better to have the first two examples
equivalent too.

Not a big issue, but it actually has come up in practice!

Regards,
Tom McGlynn