* Use RETVAL_STRINGL instead of RETURN_STRINGL in function caca_export_string

logo filename in the example

error message when this does not work

when export fails, too

new version in PHP. it seems to work, and is more flexible than the
getopt() found in PHP 5.3+.

subset of the functionality of the .NET version; added Display::getEvent
similar to the .NET version; change Dither::bitmap to take a Canvas
object rather than a caca canvas resource as its first parameter; add
Font::Render and Font::getList methods parallel to the .NET version

this is [0, 127], rather than [0, 255]; always free the temporary
pixels copy allocated in PHP_FUNCTION(caca_dither_bitmap); fix a typo
which caused PHP_FUNCTION(caca_set_display_title) to crash due to a
failed run-time binding to "caca_set_display" (the "_title" was
missing).

(this actually happens with the cocoa driver!)