[ELF2] Determine the order of entries of symbol tables in the finalize() phase.

* Move the responsibility to call SymbolBody::setDynamicSymbolTableIndex()
  from the hash table to the dynamic symbol table.
* Hash table is not longer responsible for filling the dynamic symbol table.
* The final order of symbols of both symbol tables is set before writing
  phase starts.
* Remove repeaded scan of the symbol table during writting SymbolTableSection.

Differential Revision: http://reviews.llvm.org/D13911

llvm-svn: 250864