add layer sps/pps to decoder context
Merge pull request #599 from licaiguo/add-sps-pps-for-each-layer

add layer sps/pps to decoder context
add usagetype setting for screen content
fix ios encDemo build
Merge pull request #601 from volvet/fix-ios-build

fix ios encDemo build
Merge branch 'master' of https://github.com/cisco/openh264
fix typo
Merge pull request #600 from ruil2/vp_console

add usagetype setting for screen content
Merge branch 'master' of https://github.com/cisco/openh264