fix tutorial installation

doc/Makefile.am

@@ -4,11 +4,11 @@ EXTRA_DIST = $(man_MANS) Doxyfile
 DISTCLEANFILES = \
   microhttpd.cps \
   microhttpd.dvi \
-  tutorial.cps \
-  tutorial.dvi
+  microhttpd-tutorial.cps \
+  microhttpd-tutorial.dvi
 info_TEXINFOS = \
   microhttpd.texi \
-  tutorial.texi
+  microhttpd-tutorial.texi
 microhttpd_TEXINFOS = \
   chapters/basicauthentication.inc \
   chapters/bibliography.inc \