add comment for __ksymtab_strings case

Signed-off-by: Seth Jennings <sjenning@redhat.com>
add error for sym value != 0

For a local object or function symbol, we expect that
the section offset, sym.st_value, be 0 because we used
-ffunction-sections and -fdata-section during compile.

If value != 0, it undermines assumptions we make and
should return an error.  Exceptions should be handled
on a case by case basis, like __ksymtab_strings.

Signed-off-by: Seth Jennings <sjenning@redhat.com>
fixup comment

Signed-off-by: Seth Jennings <sjenning@redhat.com>
Merge pull request #52 from spartacus06/fixes

add a few comments and st_value !=0 error