Remove an unused error code

I don't see this error code being useful - working slowly hardly
would be a reason for the library to return and fail to do what
it was asked to do, so normal functions would never actually return
this code.
add scene change detector for further extension
remove black space at lineend
reoranize common to inc/src/x86/arm
add missing build files
Merge pull request #540 from licaiguo/reorgcommon-pr

reorganize common to inc/src/x86/arm
disable most warnings produced by -Wall
Merge pull request #535 from volvet/add-scene-change-detector

Add scene change detector
add screen change detector for desktop share
remove blank space
Modify xcode project to fit common reorg.
Merge pull request #543 from zhilwang/reorgcommon-xcode

Modify xcode project to fit common reorg.
        use the same frame type EVideoFrameType in encoder internal
Remove unnecessary/superfluous parentheses in slice_multi_threading.cpp
fix most of the warnings
Merge pull request #544 from ruil2/encoder_update

        use the same frame type EVideoFrameType in encoder internal
Merge pull request #542 from volvet/add-scene-change-detector-screen

Add scene change detector screen
Automatically pick the latest installed iOS SDK when building with make

This avoids having to update the makefile just to change the SDK
version whenever the iOS SDK is updated (since the previous
version is removed on updates).
Merge pull request #545 from mstorsjo/remove-extra-parentheses

Remove unnecessary/superfluous parentheses in slice_multi_threading.cpp
add screen detector in builder