The new iPhone 3G S contains a PowerVR SGX graphics core, according to a new report, which also suggests that the new OpenGL ES 2.0 features may cause difficulties for game developers. Citing people familiar with the matter, AppleInsider reports that the new iPhone contains the new PowerVR SGX chip from Imagination Technologies, which has been integrated into the handset’s system-on-a-chip, manufactured by Samsung. Prior reports had suggested…