Failing RTL test with ICU on Fedora

[springmeyer]

Built Mapnik on Fedora(https://gist.github.com/3427021) and seeing a curious RTL visual test failure that likely has to do with ICU version. This is important because the main OSM server runs Fedora I think.

Visual text rendering summary: Failed: 183 different pixels:
    /tmp/mapnik-visual-images/rtl-point-200-agg.png (actual)
    tests/visual_tests/images/rtl-point-200-reference.png (expected)

Expected:

Actual:

[springmeyer]

yum info libicu gives:

Installed Packages
Name        : libicu
Arch        : x86_64
Version     : 4.2.1
Release     : 9.9.amzn1
Size        : 19 M
Repo        : installed
From repo   : amzn-main
Summary     : International Components for Unicode - libraries
URL         : http://www.icu-project.org/
License     : MIT and UCD and Public Domain
Description : The International Components for Unicode (ICU) libraries provide
            : robust and full-featured Unicode services on a wide variety of
            : platforms. ICU supports the most current version of the Unicode
            : standard, and they provide support for supplementary Unicode
            : characters (needed for GB 18030 repertoire support).
            : As computing environments become more heterogeneous, software
            : portability becomes more important. ICU lets you produce the same
            : results across all the various platforms you support, without
            : sacrificing performance. It offers great flexibility to extend and
            : customize the supplied services.

[herm]

This might happen when the "rtl" property in string_info is incorrectly initalized.
The code depends on ICU version, but your version should be recent enough.
You can try adding debug output here:
https://github.com/mapnik/mapnik/blob/master/src/font_engine_freetype.cpp#L314-319

[herm]

This problem is almost certainly fixed by the RTL-aware rewrite of the line breaking code.
Refs #1428.