fix level_prefix too large in residual decoding
name pre-process steps
remove unused temporal ID info in decoder API
Merge pull request #291 from volvet/name_process_step

give right name to pre-process step1 and step3
    encoder interface update step1
negative data with left shift, use cast or multiplication instead
Merge pull request #293 from ruil2/interface_step1

    encoder interface update step1 --- review request #75
Merge pull request #295 from huili2/dec_api_rm_tl

remove unused temporal ID info in decoder API
merge the calculate
Merge pull request #294 from huili2/neg_left_shift

negative data with left shift, use cast or multiplication instead
Merge pull request #292 from huili2/level_prefix

fix level_prefix too large in residual decoding
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