Remove stub interfaces for hw decoding

There is no implementation available for actually doing decoding
in HW.
fix level_prefix too large in residual decoding
move alloc spatial picture and free spatial picture to CWelsPreProcess
add update spatial pictures method too CWeslPreProcess
move spatial picture related variable to CWelsPreProcess
correct code style
Merge pull request #286 from mstorsjo/remove-hw-decode

Remove stub interfaces for hw 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
update to the last commit: interface change
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
add refine mc.cpp on decoder
1. remove unecessary init
2. add static to constant function pointer array
fix build fail on osx