RFC: fix latent bug in syms_from_objfile_1

[Tom Tromey <tromey@redhat.com>]

I recently upgraded to Fedora 18.  I randomly see this from gdb:

    warning: no loadable sections found in added symbol-file system-supplied DSO at 0x7ffff7ffd000

I tracked this warning down to a buglet in syms_from_objfile_1, which
references addrs->other[0] without first checking addrs->num_sections.

This patch fixes the problem.

Built and regtested on x86-64 Fedora 18.
This actually improves the test results for me by removing a number of
bogus FAILs caused when the warning is emitted.

Any comments?

Tom

2013-03-20  Tom Tromey  <tromey@redhat.com>

	* symfile.c (syms_from_objfile_1): Check num_sections before
	calling addr_info_make_relative.

Index: symfile.c
===================================================================
RCS file: /cvs/src/src/gdb/symfile.c,v
retrieving revision 1.367
diff -u -r1.367 symfile.c
--- symfile.c	14 Mar 2013 20:26:19 -0000	1.367
+++ symfile.c	20 Mar 2013 18:19:42 -0000
@@ -997,7 +997,7 @@
 
      We no longer warn if the lowest section is not a text segment (as
      happens for the PA64 port.  */
-  if (addrs && addrs->other[0].name)
+  if (addrs && addrs->num_sections > 0 && addrs->other[0].name)
     addr_info_make_relative (addrs, objfile->obfd);
 
   /* Initialize symbol reading routines for this objfile, allow complaints to