libdwfl: Move dwz alt multi file searching to find_debuginfo callback.

Don't hard code the Dwarf dwz alt multi file search but allow the user
to override it through the standard Dwfl_Callbacks. Also move ownership
completely to the user of dwarf_setalt by removing free_alt from Dwarf
and adding alt, fd and elf fields to Dwfl_Module. Add a relative .dwz
file test case.

Signed-off-by: Mark Wielaard <mjw@redhat.com>
diff --git a/tests/ChangeLog b/tests/ChangeLog
index ff396d5..f180fe4 100644
--- a/tests/ChangeLog
+++ b/tests/ChangeLog
@@ -1,3 +1,8 @@
+2014-05-01  Mark Wielaard  <mjw@redhat.com>
+
+	* run-readelf-dwz-multi.sh: Add tests with alt debug files in .dwz
+	subdir.
+
 2014-04-30  Mark Wielaard  <mjw@redhat.com>
 
 	* buildid.c, buildid.sh, testfile42_noshdrs.bz2: New files.