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.
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.
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
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