Do some kind of justification on this line.
Normally does full justification: adds spaces to the line to make it end at
the column given by `current-fill-column'.
Optional first argument HOW specifies alternate type of justification:
it can be `left', `right', `full', `center', or `none'.
If HOW is t, will justify however the `current-justification' function says to.
If HOW is nil or missing, full justification is done by default.
Second arg EOP non-nil means that this is the last line of the paragraph, so
it will not be stretched by full justification.
Third arg NOSQUEEZE non-nil means to leave interior whitespace unchanged, otherwise it is made canonical.