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 [email protected] Review URL: https://codereview.chromium.org/614683004