Shift positions for lineBreakType

Shift positions for lineBreakType

to keep them consistent with positions for all other flags.
This changes the internal behavior so that attributes[0].lineBreakType now means
"break opportunity at start of the text (before the first character in the string)"
and is always assigned with HB_NoBreak to conform rule LB2
(see http://www.unicode.org/reports/tr14/#LB2).

The current implementation is based on the sample implementation from tr14
that aimed to be as simple as possible rather than to be optimal.
From now, we can use pieces of the attributes array "as is"
without having to adjust some positions. Or we can analize some long text
by chunks (e.g. paragraph by paragraph) and consume less memory.

This introduces a minor overhead that will be eliminated shortly.

Change-Id: Ic873a05a9d5203b1c3d5aff2e4445a3f034c4bd2
Reviewed-by: Lars Knoll <lars.knoll@nokia.com>