nasm: use OWORD vs DQWORD

nasm knows only OWORD.  yasm knows both OWORD and DQWORD.

Provide nasm compatibility.  No binary change by this patch with yasm on
{x86_64,i686}-fedora13-linux-gnu.  Few longer opcodes with nasm on
{x86_64,i686}-fedora13-linux-gnu have been checked as safe.

Change-Id: I62151390089e90df9a7667822fa594ac20b00e78
1 file changed