fix compile warnings
add funtion pointer for search methods
add reference frame managment for screen content [still in progress]
Merge pull request #615 from volvet/clean-warning

fix compile warnings
Merge pull request #619 from ruil2/vp_dpb

add reference frame managment for screen content [still in progress]
Merge pull request #616 from sijchen/fme_merge81

[Encoder ME] add function pointer for search methods
[Encoder UT] add expGolom UT and encoder trace modification
Merge pull request #620 from JuannyWang/expNew

[Encoder UT] add expGolom UT and encoder trace modification
    add LTR mark
Merge pull request #622 from ruil2/dpb_ltr

add LTR processing in reference frame management
Merge branch 'master' of https://github.com/cisco/openh264