build: Add common CLEANFILES and DISTCLEANFILES to common-rules.mk.

By adding common CLEANFILES and DISTCLEANFILES variables to
common-rules.mk, we can remove these from most other Makefiles, and
also clean files more consistently.

Note that bin_PROGRAMS are already cleaned by 'make clean', so I
removed cases where these were unnecessarily added to CLEANFILES.

java/examples/Makefile.am

@@ -23,10 +23,8 @@ EXTRA_DIST = \
 	InspectVM.java \
 	guestfs-java.pod
 
-CLEANFILES = \
-	*.class \
-	guestfs-java.3 \
-	stamp-guestfs-java.pod
+CLEANFILES += \
+	*.class
 
 man_MANS = guestfs-java.3
 noinst_DATA = $(top_builddir)/website/guestfs-java.3.html