all TLS base are belong to TLS offset
all TLS base are belong to TLS offset

plus additional nits:
* disallow leave instruction in yet another place
* gen_lowpart for simple plus arithmetic on symbols

Review URL: http://codereview.chromium.org/554080

git-svn-id: 721b910a23eff8a86f00c8fd261a7587cddf18f8@1402 fcba33aa-ac0c-11dd-b9e7-8d5594d729c2

nacl-webkit/native_client,nacl-webkit/native_client,nacl-webkit/native_client,nacl-webkit/native_client,sbc100/native_client,nacl-webkit/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client