add me function pointers for screen contents
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.
enable Scroll detection into workflow
Fix QP<18 dequant UT bug at encoder side
This should be UT for QP<12.
Clarify a comment about MSVC parameters to fix building gtest

The temporary bug in gtest has now been fixed, but we still can keep
using the current way of fixing MSVC 2012 builds instead of switching
to the solution used previously.
Merge pull request #856 from mstorsjo/clarify-comment

Clarify a comment about MSVC parameters to fix building gtest
Merge pull request #831 from sijchen/md_merge144

[Encoder ME] Add ME function assignment for Screen Content Coding
Merge pull request #853 from dongzha/FixEncUTDequantBugMaster

Fix encoder dequant Unit Test bug for master
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.
Merge pull request #844 from lyao2/scroll_detection

enable Scroll detection into workflow
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