php 7 compability

After checking with https://www.ads-software.com/plugins/php-compatibility-checker/

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FILE: /home/seyfer/www/MineProjects/seyferseed.ru/wp-content/plugins/wordpress-bootstrap-css/inc/Less.php/SourceMap/Base64VLQ.php
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FOUND 3 ERRORS AFFECTING 1 LINE
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156 | ERROR | Bitwise shifts by negative number will throw an ArithmeticError in PHP 7.0
156 | ERROR | Bitwise shifts by negative number will throw an ArithmeticError in PHP 7.0
156 | ERROR | Bitwise shifts by negative number will throw an ArithmeticError in PHP 7.0
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FILE: /home/seyfer/www/MineProjects/seyferseed.ru/wp-content/plugins/wordpress-bootstrap-css/inc/Less.php/Parser.php
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FOUND 0 ERRORS AND 3 WARNINGS AFFECTING 3 LINES
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470 | WARNING | INI directive ‘mbstring.internal_encoding’ is deprecated since PHP 5.6
471 | WARNING | INI directive ‘mbstring.internal_encoding’ is deprecated since PHP 5.6
478 | WARNING | INI directive ‘mbstring.internal_encoding’ is deprecated since PHP 5.6
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FILE: /home/seyfer/www/MineProjects/seyferseed.ru/wp-content/plugins/wordpress-bootstrap-css/views/widgets/bootstrapcss_common_widgets.php
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FOUND 0 ERRORS AND 1 WARNING AFFECTING 1 LINE
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1 | WARNING | No PHP code was found in this file and short open tags are not allowed by this install of PHP. This file may be using short open tags but PHP does not allow them.
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