nasm: avoid relative include paths

nasm does not automatically assume the source's directory also for its
include files.

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:	I386efa0cca5d401193416c11bd7363a283541645