Make freetype/pango the default option on Linux

[Felipe Heidrich]

Hello,

Please see:
https://javafx-jira.kenai.com/browse/RT-35221

For 8u20, we would like to make Freetype and Pango the default option for handling text on Linux (replacing T2K and ICU respectively).

Notes:
- Windows and Mac already use native technologies for handling text by default (DirectWrite and CoreText respectively).
- Open-builds, which never include T2K, were already using Freetype.
- Differently than T2K and ICU, which we ship as part of JavaFX. Freetype and Pango are expected to be available on the system.
- If Freetype is not available on the system, T2K will be used instead  automatically.
- If Pango is not available on the system, Freetype will still be used for rendering text. But complex text support will not work.
- The user can set -Dprism.text=t2k to force T2K to be used. Note: this is not an official API, but good for testing at times.
 
Let me of any concerns you might have.


Ah, if anyone would like to provide us a Harfbuzz implementation that would be great.
See PangoGlyphLayout.java and pango.c as reference.

Regards,
Felipe