Use GetDefaultParams instead of memset to initialize SEncParamExt in the console test app

Most of the default parameters still are overwritten with hardcoded
values in FillSpecificParameters though, but this makes sure that
defaults are applied for any new fields at least.
Only force iLoopFilterDisableIdc to 2 if multithreading has been enabled

Previously these lines were within an #ifdef MT_ENABLED block,
but now that threading is enabled by default, we should probably
only do it if threading has been requested.
Debug for Chroma InvHadamard Dequant error
refactor code to eliminate potential div by 0
Modify the unit test for WelsDequantIHadamard2x2Dc
add missing ASM in EC
Merge pull request #1061 from mstorsjo/welsenc-init-defaults

Use GetDefaultParams instead of memset to initialize SEncParamExt in the console test app
Merge pull request #1076 from lyao2/RCdiv

refactor code to eliminate potential div by 0, review at: https://rbcommons.com/s/OpenH264/r/595/
Merge pull request #1060 from mstorsjo/loopfilter-multithreading

Only force iLoopFilterDisableIdc to 2 if multithreading has been enabled
Merge pull request #1080 from huili2/enable_ASM_EC

add missing ASM in EC
Merge pull request #1075 from HaiboZhu/Debug_InvHadamard_Chroma

Debug for chroma inv-hadamard dequant mismatch error