Support missing "*" in file:read formats

[daurnimator]

Support missing * in file:read and file:lines formats.

$ lua -e 'print(io.stdin:read("a"))' <<< test
test

$ lua5.1 -l compat53 -e 'print(io.stdin:read("a"))' <<< test
lua5.1: (command line):1: bad argument #1 to 'read' (invalid option)
stack traceback:
    [C]: ?
    [C]: in function 'read'
    (command line):1: in main chunk
    [C]: ?

[daurnimator]

Added with 6190ad9...7baf0a3