Cleanup the crtbegin/crtend handling.
Cleanup the crtbegin/crtend handling.

Most of these were already available in the "newlib"
and native directories.

Also, added proper shim support for x86-64


BUG= http://code.google.com/p/nativeclient/issues/detail?id=2745 
TEST= cd tests/pnacl_ld_experiments; make run1.x8632
Review URL: https://chromiumcodereview.appspot.com/10399005

git-svn-id: 721b910a23eff8a86f00c8fd261a7587cddf18f8@8591 fcba33aa-ac0c-11dd-b9e7-8d5594d729c2

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