Wrong highlighting of the text before the beginning of a module if file starts with a keyword

[florentc]

When a file directly starts with a TLA+ keyword or operator, the text zone before the beginning of the module -------- MODULE modulename -------- is not highlighted as a comment region as it should be but as regular TLA+ code instead.

• keyword random text causes the issue
• keyword random text does not (because of the whitespece)
• keywordrandom text does not (not a keyword)