(f90-get-beg-of-line): Removed and replaced with line-beginning-position.

(f90-get-beg-of-line): Removed and replaced with line-beginning-position.
(f90-get-end-of-line): Removed and replaced with line-end-position.
(f90-current-indentation): current-column was superfluous, removed.
(f90-match-piece): Removed and replaced with match-string.
(f90-get-present-comment-type): Use match-string rather than
buffer-substring.
(f90-match-end): Use line-beginning-position, line-end-position rather than
beginning-of-line, end-of-line.