fixed the dynamic link problem with tengine in i686 box.

The compiler needs to know that __sync_add_and_fetch_4 is ok,
and this requires an instruction that didn't exist on i586 or i386.
Merge pull request #504 from yaoweibin/march_i686

fixed the dynamic link problem with tengine in i686 box.
config: fix typo in FLAG_MARCH
Merge branch 'master' into trunk-tracking