llvm-objdump/COFF: Print load configuration table.

Load Configuration Table may contain a pointer to SEH table. This patch is to
print the offset to the table. Printing SEH table contents is a TODO.

The layout of Layout Configuration Table is described in Microsoft PE/COFF
Object File Format Spec, but the table's offset/size descriptions seems to be
totally wrong, at least in revision 8.3 of the spec. I believe the table in
this patch is the correct one.