Add pkg-config file.
fix Rc int32_t bitrate overflow
add encoder cabac support
Merge pull request #1456 from dongzha/fixRCOverFlow

fix Rc int32_t bitrate overflow
Merge pull request #1455 from zaheerm/pkgconfig

Add pkg-config file.
Fix openh264.pc file installation

If there's no pkgconfig subdirectory yet in our
install prefix, create it first, otherwise we'll
end up with a file called 'pkgconfig' instead.
Add .pc file generation to PHONY targets as version change in Makefile needs to cause a rebuild.
Merge pull request #1459 from tp-m/pkgconfig-install-fix

Fix openh264.pc file installation
Merge pull request #1460 from zaheerm/pkgconfig

Add .pc file generation to PHONY targets
    add updated documents from v1.2
Merge pull request #1457 from ruil2/enc_cabac

add encoder cabac support
for reference selection under screen:
1, ref_list_mgr_svc.cpp, Ln314: fix a wrong DeleteLTRFromLongList which should not be used under screen strategy
2, ref_list_mgr_svc.cpp, Ln910: remove the frame which is furthest in distance to the current frame in ref list
3, wels_preprocess.cpp: use scene LTR ref list when the current frame is scene LTR
-, ref_list_mgr_svc.cpp, Ln811: add DEBUG trace
reviewed at: https://rbcommons.com/s/OpenH264/r/870/
update VERSION in Makefile
set option for ParamExt----random cases
Don't stash the cabac state into the SBitStringAux buffer

This fixes crashes on some platforms, and fixes valgrind
errors.
Remove the pBuffer parameter from the entropy encoder stash functions

The parameter didn't make sense since it only pointed to the
pSliceBsa field, which isn't what should be used to stash
the cabac context.
Revert unrelated changes to MSVC project file nasm commands

The cabac encoder commit accidentally changed some of the nasm
commands in the MSVC project file, that were previously
made consistent in b17e9bb32 and 7720f2cc5.
Merge pull request #1467 from mstorsjo/cabac-stash-fix

Don't stash the cabac state into the SBitStringAux buffer
Merge pull request #1464 from mstorsjo/unify-msvc-nasm

Revert unrelated changes to MSVC project file nasm commands
Merge pull request #1466 from shihuade/APIUTV1.5

set option for ParamExt----random cases