v4.000

        [ THIS MIGHT BREAK YOUR CODE ]
        - the SingleEncoding plugin to force one consistent =encoding
        - ...is now enabled, for UTF-8, in the default configuration
require recent-enough Mixin-Linewise
pick up SingleEncoding encoding from document if possible
normalize utf8 to UTF-8
fix prereq name
v4.001

        - SingleEncoding now accepts found =encodings as long as they match,
          unless the plugin's encoding attribute was set explicitly
Mixin::Linewise 0.101 seems to stink; refuse it
Merge branch 'encoding'
v4.002

        [ THIS MIGHT BREAK YOUR CODE ]
        - stable release of previous v4 changes