Move doc/logo/xz-logo.png to "doc" and Doxygen footer to "doxygen".

The footer isn't a complete HTML file so having it in the doxygen
directory is a tiny bit clearer.

Makefile.am

@@ -61,7 +61,7 @@ endif
 EXTRA_DIST = \
 	po4a \
 	extra \
-	doc/logo \
+	doc/xz-logo.png \
 	dos \
 	doxygen \
 	windows \

doxygen/Doxyfile

@@ -61,7 +61,7 @@ PROJECT_BRIEF          =
 # pixels and the maximum width should not exceed 200 pixels. Doxygen will copy
 # the logo to the output directory.
 
-PROJECT_LOGO           = ../doc/logo/xz-logo.png
+PROJECT_LOGO           = ../doc/xz-logo.png
 
 # The OUTPUT_DIRECTORY tag is used to specify the (relative or absolute) path
 # into which the generated documentation will be written. If a relative path is
@@ -1246,7 +1246,7 @@ HTML_HEADER            =
 # that doxygen normally uses.
 # This tag requires that the tag GENERATE_HTML is set to YES.
 
-HTML_FOOTER            = ../doc/logo/copyright.html
+HTML_FOOTER            = footer.html
 
 # The HTML_STYLESHEET tag can be used to specify a user-defined cascading style
 # sheet that is used by each HTML page. It can be used to fine-tune the look of