Merge changes from topic 'dead-code'

* changes:
  yv12config.c: remove dead CONFIG_ALPHA code
  vp9_encoder.c: remove unused macro
  vpx_mem.c: remove unused macro
  vp9_svc_layercontext.c: relocate a macro definition
  vp9_encoder.c: protect SNPRINT* macros w/CONFIG check
  vp9_aq_360.c: remove some unused macros
  vp9_diamond_search_sad_avx.c: rename (un)likely macros
  vp9_resize.c: add missing include
  vp9_aq_complexity.c: remove unused macros
  vp9_detokenize.c: remove unused macros