Update lessphp to 2cc77e3c7b

Source:
* https://github.com/leafo/lessphp/compare/b7cd5c79e8...2cc77e3c7b
* https://github.com/leafo/lessphp/blob/2cc77e3c7b9e84cf30ca64fccf2a45a84fbcf0d3/lessc.inc.php

Updates:
* 84b1fda0d4 Set visibility of lessc::compileValue to 'public'

Change-Id: I499ddb01a662896fdcfe56d18021de5314e4d5d2