Fix many many problems in xtext.c related to character width.

Fix many many problems in xtext.c related to pixel width of characters
and inaccuracies on resizing due to bolding and italicizing and font changing.
   * Rework multiline logic to use a GSList, not an array
   * Remove all multibyte booleans; everything is potentially multibyte
      - Except for gtk_xtext_get_word(), which needs special attention
   * Enhance pango work for bold and italics (attr_list -> attr_lists[4])
   * Enhance gtk_xtext_strip_color () to save bold, italics info
   * Involve emphasis information in all pixel-width calculations
   * Rework find_x () to account for emphasis info in widths