Support for coarray syntax

[hheinzer]

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With the new Fortran coarrays, formatting results are slightly awkward:

real, allocatable :: a(:)[:]

is formatted into

real, allocatable :: a(:) [:]

Every time the [] operator appears, fprettify inserts a space before it.

The syntax for coarrays requires you to always put an index range () before using the codimension []. This might simplify an implementation.