Pass a symbol table to getRelocationSymbol instead of returning one.

Pass a symbol table to getRelocationSymbol instead of returning one.

This removes a report_fatal_error from library and avoids checking a
section property for every section entry.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@246656 91177308-0d34-0410-b5e6-96231b3b80d8