[grilo] docs: fix make distclean

[Victor Toso de Carvalho <victortoso src gnome org>]

commit f7fa152f5b697a4fcd8fc9faf9d306402a1ee928
Author: Victor Toso <me victortoso com>
Date:   Thu Aug 24 17:26:56 2017 +0200

    docs: fix make distclean
    
    Otherwise we'll get:
    
    ERROR: files left in build directory after distclean:
    ./doc/grilo/grilo-scan.o
    ./doc/grilo/efficient-metadata-resolution.c
    ./doc/grilo/searching.c
    ./doc/grilo/configuring-plugins.c
    ./doc/grilo/browsing.c
    ./doc/grilo/multivalues.c

 doc/grilo/Makefile.am |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/doc/grilo/Makefile.am b/doc/grilo/Makefile.am
index 4f2ed61..5c186a3 100644
--- a/doc/grilo/Makefile.am
+++ b/doc/grilo/Makefile.am
@@ -118,7 +118,7 @@ EXTRA_DIST +=
 # Files not to distribute
 # for --rebuild-types in $(SCAN_OPTIONS), e.g. $(DOC_MODULE).types
 # for --rebuild-sections in $(SCAN_OPTIONS) e.g. $(DOC_MODULE)-sections.txt
-#DISTCLEANFILES +=
+DISTCLEANFILES = *.o *.stamp $(DOC_MODULE).* $(program_listings)
 
 # Comment this out if you want your docs-status tested during 'make check'
 if ENABLE_GTK_DOC