Section 15.4: tune text about history of redirect status codes

[reschke]

|  *Note:* In HTTP/1.0, the status codes 301 (Moved Permanently)
|  and 302 (Found) were defined for the first type of redirect
|  ([RFC1945], Section 9.3).  Early user agents split on whether
|  the method applied to the redirect target would be the same as
|  the original request or would be rewritten as GET.  Although
|  HTTP originally defined the former semantics for 301 and 302
|  (to match its original implementation at CERN), and defined 303
|  (See Other) to match the latter semantics, prevailing practice
|  gradually converged on the latter semantics for 301 and 302 as
|  well.  The first revision of HTTP/1.1 added 307 (Temporary
|  Redirect) to indicate the former semantics of 302 without being
|  impacted by divergent practice.  For the same reason, 308
|  (Permanent Redirect) was later on added in [RFC7538] to match
|  301.  [...]

I had to read this text several times to find a way to understand it
that seems to make sense to me (but might still be wrong!).
I think part of my confusion is that the word "former" is being used in
two different senses (the first of the two choices, and the
historical/earlier version). Perhaps it's more clear to just talk about
"method rewriting" (and not rewriting) instead of using the overloaded
term.