Linux now using the PowerVR SDK for the OpenGL | ES 2.0 implementation

|BUILD CONFIGURATION|
[Linux]
* Added POWERVRSDK_ROOT to the include and library paths

|SOURCE|
[Common/GLES2Extensions]
* Added OES to the end of the extensions string values
[Common/GLES2Renderer]
* Moved the OpenGL | ES 2.0 extensions to Initialise
* OpenGL | ES 2.0 information is printed to the console at startup
[Common/LinuxEGLWindow]
* The EGL version is printed out when created and error codes are handled when
  initialising EGL