Revert "[directfb] add alsa-lib to DEPENDS"

This reverts commit 97e735418c8e19a25b6d72d003566974fd7c44a5.
Revert "add support for raspberrypi, enable gles2 and egl, update directfbrc"

This reverts commit 4142b90ecf785e6ac0ba0e058c849b2a6a5b147e.
Revert "add support for machine-specific recipe appends"

This reverts commit e77c621d4840745cccd89897d663d888b6f1459d.