bitbake: [parser] Remove the "data" from feeder, evaluate after parsing a file

bitbake: [parser] Remove the "data" from feeder, evaluate after parsing a file

Evaluate the statements after having parsed one file. This is
referred to as "entwirren" and we can remove the direct evaluation
and postpone a bit, in the future we can use a cached copy instead
of parsing the original.

Signed-off-by: Richard Purdie <rpurdie@linux.intel.com>