pdf_create_obj() now returns the object number

source/texk/web2c/luatexdir/image/writeimg.w

source/texk/web2c/luatexdir/image/writejbig2.w

source/texk/web2c/luatexdir/image/writepng.w

source/texk/web2c/luatexdir/lua/limglib.c

source/texk/web2c/luatexdir/lua/lpdflib.c

source/texk/web2c/luatexdir/pdf/pagetree.w

source/texk/web2c/luatexdir/pdf/pdfannot.w

source/texk/web2c/luatexdir/pdf/pdfdest.w

source/texk/web2c/luatexdir/pdf/pdffont.w

source/texk/web2c/luatexdir/pdf/pdfgen.w

source/texk/web2c/luatexdir/pdf/pdflink.w

source/texk/web2c/luatexdir/pdf/pdfobj.w

source/texk/web2c/luatexdir/pdf/pdfoutline.w

source/texk/web2c/luatexdir/pdf/pdftables.h

source/texk/web2c/luatexdir/pdf/pdftables.w

source/texk/web2c/luatexdir/pdf/pdfxform.w