introduce os.EOF and io.ErrUnexpectedEOF.
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
diff --git a/src/pkg/io/bytebuffer.go b/src/pkg/io/bytebuffer.go
index 000c053..11c8a1a 100644
--- a/src/pkg/io/bytebuffer.go
+++ b/src/pkg/io/bytebuffer.go
@@ -103,10 +103,10 @@
 }
 
 // ReadByte reads and returns the next byte from the buffer.
-// If no byte is available, it returns error ErrEOF.
+// If no byte is available, it returns error os.EOF.
 func (b *ByteBuffer) ReadByte() (c byte, err os.Error) {
 	if b.off >= len(b.buf) {
-		return 0, ErrEOF;
+		return 0, os.EOF;
 	}
         c = b.buf[b.off];
 	b.off++;