add go course pdf files to doc/ for godoc to serve.
fix links to point to those files.
R=rsc
DELTA=7 (4 added, 0 deleted, 3 changed)
OCL=35972
CL=35981
remove io.ErrEOF.
rename io.FullRead to io.ReadFull, to match
ReadAtLeast and ReadAll.
remove io.FullReader, because it is now unused.
R=r
DELTA=295 (88 added, 105 deleted, 102 changed)
OCL=30544
CL=30588