add layer sps/pps to decoder context
Merge pull request #599 from licaiguo/add-sps-pps-for-each-layer

add layer sps/pps to decoder context
add usagetype setting for screen content
fix ios encDemo build
Merge pull request #601 from volvet/fix-ios-build

fix ios encDemo build
Add alternative search methods
fix typo
add scene change for screen content
Merge pull request #600 from ruil2/vp_console

add usagetype setting for screen content
Merge pull request #603 from ruil2/vp_update2

add scene change for screen content

Approved by Sijia.
clean multi-threading macro
    use WelsLog instead of fprintf to have a unified trace output
Merge pull request #604 from ruil2/vp_trace

    use WelsLog instead of fprintf to have a unified trace output
Merge pull request #602 from sijchen/fme_merge22

[Encoder ME] Add alternative search methods
fix bug of assign data
Merge pull request #606 from huili2/PredUT_fix

fix bug of assign data of UT code
Add EncoderMB UT test file, and reformat UT files.
Merge pull request #607 from ganyangbbl/encUT_EncoderMB2

Add EncoderMB UT test file, and reformat encoder UT files.
Merge pull request #605 from volvet/clean_mt_macro

clean multi-threading macro
    use function pointer in reference frame management