Correctly document when getopt returns EOF and '?', and some other

minor cleanup.

lib/libc/stdlib/getopt.3

@@ -122,7 +122,9 @@ The
 function
 returns an
 .Dv EOF
-when the argument list is exhausted, or a non-recognized
+when the argument list is exhausted, or 
+.Ql ?
+if a non-recognized
 option is encountered.
 The interpretation of options in the argument list may be canceled
 by the option
@@ -142,10 +144,10 @@ If the
 function encounters a character not found in the string
 .Va optarg
 or detects
-a missing option argument it writes an error message and returns
-.Ql ?
-to the
-.Em stderr .
+a missing option argument it writes an error message to the
+.Em stderr
+and returns
+.Ql ? .
 Setting
 .Va opterr
 to a zero will disable these error messages.