Add eof to MemReader and BufReader

It's easy to figure out and useful as a sanity check sometimes.
auto merge of #11437 : sfackler/rust/mem-eof, r=alexcrichton

It's easy to figure out and useful as a sanity check sometimes.
Removed obsolete 'e' prefix on ty_evec and ty_estr.
Removed free_glue from tydesc (the code is still generated, but inlined in drop_glue).
Use the right type for self in methods and remove obsoleted items.
Fixes #7411, #10615.