add refine mc.cpp on decoder
1. remove unecessary init
2. add static to constant function pointer array
fix build fail on osx
Merge pull request #296 from ruil2/build_osx

fix build fail on osx
Fix building with MT_DEBUG enabled after the encoder interface update

There is no struct named SMulSliceOption any longer.
Silence building libwels.a building with V=0
Merge pull request #300 from mstorsjo/silent-make

Silence building libwels.a building with V=0
Merge pull request #299 from mstorsjo/fix-renamed-struct

Fix building with MT_DEBUG enabled after the encoder interface update
use temporal layer num and remove gop size in external configure
Remove useless ifdefs

This is in practice always enabled on all currently supported
platforms.
Merge pull request #302 from mstorsjo/remove-useless-ifdef

Remove useless ifdefs
Merge pull request #297 from licaiguo/refine-mc.cpp

add refine mc.cpp on decoder
Merge pull request #301 from ruil2/temporal_num

use temporal layer num and remove gop size in external configure-- review request #94
Merge remote-tracking branch 'upstream/master' into travis.osx