Add missing OSL surface shader to api headers.
Add missing OSL surface shader to api headers.

aytekaman/appleseed,appleseedhq/appleseed,appleseedhq/appleseed,Biart95/appleseed,dictoon/appleseed,est77/appleseed,Aakash1312/appleseed,dictoon/appleseed,luisbarrancos/appleseed,appleseedhq/appleseed,dictoon/appleseed,est77/appleseed,est77/appleseed,Biart95/appleseed,Biart95/appleseed,gospodnetic/appleseed,Biart95/appleseed,aytekaman/appleseed,Aakash1312/appleseed,glebmish/appleseed,appleseedhq/appleseed,aytekaman/appleseed,glebmish/appleseed,appleseedhq/appleseed,aytekaman/appleseed,Vertexwahn/appleseed,Vertexwahn/appleseed,aiivashchenko/appleseed,pjessesco/appleseed,pjessesco/appleseed,glebmish/appleseed,Vertexwahn/appleseed,Aakash1312/appleseed,Biart95/appleseed,aiivashchenko/appleseed,aiivashchenko/appleseed,pjessesco/appleseed,luisbarrancos/appleseed,glebmish/appleseed,gospodnetic/appleseed,pjessesco/appleseed,luisbarrancos/appleseed,Vertexwahn/appleseed,aytekaman/appleseed,gospodnetic/appleseed,glebmish/appleseed,gospodnetic/appleseed,pjessesco/appleseed,luisbarrancos/appleseed,Aakash1312/appleseed,aiivashchenko/appleseed,est77/appleseed,dictoon/appleseed,est77/appleseed,luisbarrancos/appleseed,Vertexwahn/appleseed,dictoon/appleseed,gospodnetic/appleseed,aiivashchenko/appleseed,Aakash1312/appleseed