Revert "Make va_list a struct on X86-32 to match PNaCl."

This reverts commit 5e4e74a0ccc2757783ccf26f68cac1ef2cadb126.

Since nacl-clang was not modified this ends up being a mismatch.
Revert to match again.

BUG= https://code.google.com/p/nativeclient/issues/detail?id=3650
R=khim@google.com

Review URL: https://codereview.chromium.org/614683004
1 file changed