add interface and basic implementaion and UT for EncoderStatistics
Remove the "platform-" prefix from common shared makefiles

This makes it clearer which ones actually are real platforms
(chosen automatically or explicitly via "make ARCH=foo") and which
ones just are shared helpers.
        add a thread name for easier profiling
Merge pull request #1432 from mstorsjo/rename-makefiles

Remove the "platform-" prefix from common shared makefiles
fix crash bug of sps/pps
Merge pull request #1438 from huili2/EC_crashfix

fix crash bug of sps/pps
Merge pull request #1429 from sijchen/add_statistics1

[Encoder] add EncoderStatistics
Merge pull request #1437 from sijchen/after_review2

[Encoder] add a thread name for easier profiling
Merge remote-tracking branch 'upstream/master' into travis.osx