* Modify php bloc headers in samples programs
* Add list of import/export formats in examples/drivers.php

given gd resource.

* Add php binding for "caca_create_dither"
* Add new sample program "dithering.php"

resources such as gd resouces
* Add test for presence of gd development files in config.m4
* Rename php function caca_dither_bitmap in caca_dither_bitmap_gd

* Add binding for 2 new functions
* Fix a bug in examples/example1.php

* Improve examples/demo.php

* Add php binding for 13 new functions