PNaCl: Change the sizeof va_list from 24 to 16, and the alignment from 8 to 4, to match NNaCl X86-64.
PNaCl: Change the sizeof va_list from 24 to 16, and the alignment
from 8 to 4, to match NNaCl X86-64.

Will commit utman.sh changes first, so that only the PNaCl TC builder
goes red. Once the toolchain build finishes, I'll update DEPS and the scons tests. 


Includes CLs:
http://codereview.chromium.org/7055015/
http://codereview.chromium.org/7057023/
Review URL: http://codereview.chromium.org/7038048

git-svn-id: 721b910a23eff8a86f00c8fd261a7587cddf18f8@5394 fcba33aa-ac0c-11dd-b9e7-8d5594d729c2

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