Two threading issues:

- Drawing masks in image editor requires LOCK_DRAW_IMAGE around
  ED_space_image_get* functions since they'll acquire image buffer.

  Lock is needed because viewers will be modified directly in
  compositor (see commend in draw_image_main)

- Seems that was wrong order of invalidating render result and
  viewer image invalidation happened in Composite node, which
  could easily lead to thread lock.

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@53805 954f8c5b-7b00-dc11-b283-0030488c597c
Spelling corrections

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@53806 954f8c5b-7b00-dc11-b283-0030488c597c