This refine is to remove slice number limitation in the future. The changes contains:
1. add pNalLen in Structure SWelsEncoderOutput to store each nal length
2. rename iNalLengthInByte[MAX_NAL_UNITS_IN_LAYER] to pNalLengthInByte in Structure SLayerBSInfo, the pointer point to pNalLen, like pBSBuf point to pFrameBS.
Add Sad arm64 code
Remove an unused static function

This avoids a warning with clang.

This function was added in 4bd6a3a6e8 even though nothing in
that commit actually uses it.
Add gnu assembler support.
Refine some code
Remove two unused ifdefs

Nothing in the project sets HAVE_MMX.

The commented out code for setting pSearchMethodFunc can be readded
once it's actually implemented properly.
reformat
change comment in encoder option according to issue https://github.com/cisco/openh264/issues/859
set minimum quant as 4 to avoid level code overflow
Merge pull request #842 from ganyangbbl/refine_nal2

Refine Nal length related structure
Merge pull request #858 from sijchen/md_merge145

reformat some missed style and remove unused comments
Merge pull request #864 from ruil2/enc_quant

set minimum quant as 4 to avoid level code overflow
Merge pull request #863 from dongzha/FixEncOptionMaster

change comment in encoder option according to issue cisco#859 for master
add single function for new seq detection
Merge pull request #857 from mstorsjo/remove-unused-ifdef

Remove two unused ifdefs
Merge pull request #843 from mstorsjo/remove-unused-function

Remove an unused static function
using WelsRound for all the double-int32_t conversion
Add unittest demo for android platform
not need
not need