Duplicated/overridden recipes from meta-oe and core

[kraj]

meta-atmel has duplicated few recipes from meta-oe

swig:
  meta                 3.0.12
  meta-atmel           3.0.8

cjson:
  meta-atmel           1.7.4
  meta-oe              1.7.14

first one is easy, please start using the version coming from oe-core
for second issue, I think only layer you want to depend on is oe-core
which means if you do not keep a copy of cjson in this layer then you have to
add a dependency on meta-oe which is actually preferred to status quo
because currently if meta-atmel is used then it silently overrides the version
from meta-oe since it has higher layer priority.

Other option is to try to move cjson recipe to oe-core and that way you don't
have to add dependency on meta-oe, but you still have to start using the version
from oe-core

[codrin989]

I see that libplanes depends on swig and for some reason we want 3.0.8. cjson is needed by both libplanes and libegt. @SandeepSM @ldesroches @noglitch what do you think, is it safe to upgrade these packets?