Accept Armin's documentation patch for SF bug #558179.

Adjusted some markup to make the descriptions more consistent.

Doc/lib/librfc822.tex

@@ -255,12 +255,12 @@ there is no header matching \var{name}, or it is unparsable, return
 In particular: \code{\var{m}[name]} is like
 \code{\var{m}.getheader(name)} but raises \exception{KeyError} if
 there is no matching header; and \code{len(\var{m})},
-\code{\var{m}.get(name\optional{, deafult})},
-\code{\var{m}.has_key(name)}, \code{\var{m}.keys()},
+\code{\var{m}.get(\var{name}\optional{\var{, default}})},
+\code{\var{m}.has_key(\var{name})}, \code{\var{m}.keys()},
 \code{\var{m}.values()} \code{\var{m}.items()}, and
-\code{\var{m}.setdefault(name\optional{, default})} act as expected,
-with the one difference that \method{get()} and \method{setdefault()}
-use an empty string as the default value.  \class{Message} instances
+\code{\var{m}.setdefault(\var{name}\optional{\var{, default}})} act as
+expected, with the one difference that \method{setdefault()} uses
+an empty string as the default value.  \class{Message} instances
 also support the mapping writable interface \code{\var{m}[name] =
 value} and \code{del \var{m}[name]}.  \class{Message} objects do not
 support the \method{clear()}, \method{copy()}, \method{popitem()}, or