elfcopy: fix symbol table handling when sections come after symtab/strtab

elfcopy: fix symbol table handling when sections come after symtab/strtab

  Fix a symbol table handling bug in elfcopy: elfcopy puts .symtab,
  .strtab and .shstrtab sections in the end of the output object.  If
  the input objects have more sections after any of these 3 sections,
  the section table will be reordered, and in that case the section
  symbols should be regenerated for relocations.

  The bug is triggered since newer clang puts .strtab section in the
  beginning of the object produced.

   Ticket: #525

Reported by:	royger
Obtained from:	ELF Tool Chain r3443