add interface for error concealment, to be continued
Remove the unused WELSVP_EXPORTS define
Merge pull request #651 from mstorsjo/remove-unused-define

Remove the unused WELSVP_EXPORTS define
fix colorsapce check
refine method EncodeFrame
Merge pull request #653 from volvet/fix_colorspace_check

fix colorsapce check
Merge pull request #655 from huili2/EC_interface

add interface for error concealment, to be continued
Merge pull request #654 from volvet/refine_enc_frame

refine method EncodeFrame
refine decoder side intrapred unit test, test assembly routine
only when the cpu feature can support it
Merge pull request #656 from licaiguo/refine-dec-intrapred-ut

refine decoder side intrapred unit test, test assembly routine only when the cpu feature can support it