Function: fill-region-as-paragraph

Fill the region as one paragraph.
It removes any paragraph breaks in the region and extra newlines at the end,
indents and fills lines between the margins given by the
`current-left-margin' and `current-fill-column' functions.
(In most cases, the variable `fill-column' controls the width.)
It leaves point at the beginning of the line following the paragraph.

Normally performs justification according to the `current-justification'
function, but with a prefix arg, does full justification instead.

From a program, optional third arg JUSTIFY can specify any type of
justification. Fourth arg NOSQUEEZE non-nil means not to make spaces
between words canonical before filling. Fifth arg SQUEEZE-AFTER, if non-nil,
means don't canonicalize spaces before that position.

Return the `fill-prefix' used for filling.

If `sentence-end-double-space' is non-nil, then period followed by one space does not end a sentence, so don't break a line there.