Fix sed expression due to changed LineBreak.txt file format

Hi,
maybe I am doing something wrong, but when I recently rebuilt the library I got the `lb_prop_default[]` array containing just a single value:

` { 0xFFFFFFFF, 0xFFFFFFFF, LBP_Undefined }`

My take on this is that it is due to the following reason: 

The file `LineBreak.txt` is automatically downloaded from the
following URL:

  http://unicode.org/Public/UNIDATA/LineBreak.txt

However the file format changed slightly since the 7.0.0 version;
it contains one or more spaces in front of the `#` (dash, comment)
character.

Therefore it was necessary to alter the SED expression to accept
such format:
 - add `+` character to accept one of more spaces.