glGetString + checkGLExtensions + opengl3+

[headupinclouds]

@xsacha reported a crash/error in glGetString for checkGLExtensions on Android platforms.

"looks like known issue on opengl3+" kbranigan/Simple-OpenGL-Image-Library#8

See:

ogles_gpgpu/ogles_gpgpu/common/core.cpp

Lines 361 to 385 in faf83dc

	void Core::checkGLExtensions() {
	// get string with extensions seperated by a SPACE
	string glExtString((const char*)glGetString(GL_EXTENSIONS));
	// get extensions as vector
	vector<string> glExt = Tools::split(glExtString);
	// check extensions
	// OG_LOGINF("Core", "list of extensions:");
	for (auto& it : glExt) {
	// get lowercase extension string
	string extName = it;
	transform(extName.begin(), extName.end(), extName.begin(), ::tolower);
	// OG_LOGINF("Core", "> %s", extName.c_str());
	// check for NPOT mipmapping support
	if (it.compare("gl_arb_texture_non_power_of_two") == 0
	|| it.compare("gl_oes_texture_npot") == 0) {
	glExtNPOTMipmaps = true;
	}
	}
	OG_LOGINF("Core", "NPOT mipmaps support: %d", glExtNPOTMipmaps);
	}