view_growbuf_read_until() suggestion

[Pavel Tsekov]

Hello Roland,

There is a small "bug" in the new viewer code. When the viewer is used in
growing buffer mode it incorrectly displays in the status bar ">= size"
even if the data source was exhausted and despite the fact the the
size of the whole buffer is known. Please, take a look at the attached
patch for a idea how to fix it. Of course you could find a better way to
solve this since you know the code better.