C++ PATCH for target/54908 (thread_local vs emutls)

[Dominique Dhumieres]

> > FAIL: g++.dg/tls/thread_local-wrap3.C scan-assembler _ZTH1i
> > FAIL: g++.dg/gomp/tls-wrap3.C -std=c++98  scan-assembler _ZTH1i
> > FAIL: g++.dg/gomp/tls-wrap3.C -std=c++11  scan-assembler _ZTH1i
>
> Ah, yes; those are specifically testing for the aliases that we can't 
> generate on darwin. I'll add dg-require-alias to those tests. ...

These tests still fail on x86_64-apple-darwin10 after bootstrapping 
a clean revision 195310.

Dominique