Compile on Ubuntu 18.04

[obeezzy]

• Add to ActorIKConstraint.cpp to fix error
• Add to JellyComponent.cpp to fix error

[obeezzy]

To anyone who may want to know, I had to install both clang and glfw3 to get it to build. From the root directory, I ran:

$ sudo apt-get install -y clang
$ sudo apt-get install -y libglfw3 libglfw3-dev
$ git submodule update --init --recursive
$ make -f Makefile

Also, there's a similar change for Nima-Cpp-OpenGL.