[ELF][x86-84] Add static TLS support.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@174154 91177308-0d34-0410-b5e6-96231b3b80d8
[ELF][x86-64] Implement static relocation model for TLS.

This implements the static relocation model for GOT accesses to TLS.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@174155 91177308-0d34-0410-b5e6-96231b3b80d8