Linux: added project part for QtCreator.

Allows easily setup cocos2d on Linux in QtCreator IDE.
Enabled c++0x flag, use OpenAL audio backend by default.
issue #2305:remove unneeded comment
issue #2276: Add OpenGL lua module
Merge branch 'develop' of https://github.com/cocos2d/cocos2d-x into glMoudle
Merge pull request #2983 from folecr/ccx_filesystem

Improve Android file system read performance
Merge branch 'develop' of https://github.com/cocos2d/cocos2d-x into ccx_filesystem
Merge pull request #2989 from samuele3hu/glMoudle

issue #2276: Add OpenGL lua module
Merge pull request #2990 from minggo/ccx_filesystem

fixed a compiling error of AssetsManager on Android
issue #2325: Fixing an issue that Xcode doesn't rebuild app when source file updated in dependent static library.
Merge pull request #2993 from dumganhar/iss2325-ios-workspace-dependence-fix

issue #2325: Fixing an issue that Xcode doesn't rebuild app when source file updated in dependent static library.
Share top level Makefile between emscripten, linux and nacl.

Remove the custom top level Makefile.emscripten and instead
add build-emscripten.sh which can be used like build-linux.sh
and build-nacl.sh.

Also, use the top level lib folder to store emscripten libs.
This brings it in line with the other make-based builds.
Fix emscripten build on linux

Remove the dependacy of the emscripten build on /Library/Fonts
(a darwin-only folder).  On non-darwin platforms we use the
ariel.tff that is part of TestCpp.
issue #2305: Using c++11 std::thread instead of pthread for HttpClient class.
issue #2305: Fixing a crash when error is triggered in WebSocket. Using std::lock_guard to replace lock and unlock manually.
issue #2305: Reverting to use lock and unlock for HttpClient.
issue #2305: Fixing a bug that passing wrong mutex parameter to "wait".
issue #2305: Using the old logic of "wait".
issue #2305: Sleep(50) on Win32, usleep(50000) on unix --> std::this_thread::sleep_for(std::chrono::milliseconds(50));
Merge pull request #3001 from dumganhar/iss2305-std-thread

issue #2305: Using c++11 std::thread instead of pthread for HttpClient class.