lcl_AddSpace determine the amount of space to distribute
to a portion based on its text length. Counting the number
of CJK characters prevent including codepoints that are not
visible, such as surrogate pairs or Unicode variance
selectors, by mistake.

Change-Id: Ia20a7f76ea1ea3c1f4638db865721eaa26a8c82c
Reviewed-on: https://gerrit.libreoffice.org/29616Reviewed-by: Khaled Hosny <khaledhosny@eglug.org>
Tested-by: Khaled Hosny <khaledhosny@eglug.org>