Flame bait: mod_charset_lite would decide in the mime checker phase

Flame bait: mod_charset_lite would decide in the mime checker phase
whether a conversion was required, and would stick with that decision,
even if a later handler (like CGI script) would modify the actual
MIME type returned in the response. That was fatal when an EBCDIC
machine was going to return, say, an image/gif (because the initial
MIME type would be text/plain, and only later on be set to image/gif).
But even for "ordinary" ASCII-based machines the conversion fails
if a CGI script decides to return UTF-16 data.
At the moment the following change is #if #system(bs2000), but IMHO
it should be enabled globally: I moved the conversion decision into
the filter itself (because it is the handler which does the final
decision which MIME time is tagged on the response, and we can only
evaluate its decision after it started the output generation).

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@102066 13f79535-47bb-0310-9956-ffa450edef68