progs/demos: create a texture object in lodbias.c

Before, we were using the default texture object (name=0).  This caused
the intel_generate_mipmap() path to fail since passing texture=0 to
glFramebufferTexture2DEXT() causes us to _unbind_ the texture if present.

progs/demos/lodbias.c

@@ -43,6 +43,7 @@ static GLboolean Anim = GL_TRUE;
 static GLint Bias = 0, BiasStepSign = +1; /* ints avoid fp precision problem */
 static GLint BiasMin = -400, BiasMax = 400;
 static int win = 0;
+static GLuint TexObj = 0;
 
 
 static void
@@ -214,6 +215,9 @@ static void Init( void )
 
    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
 
+   glGenTextures(1, &TexObj);
+   glBindTexture(GL_TEXTURE_2D, TexObj);
+
    if (glutExtensionSupported("GL_SGIS_generate_mipmap")) {
       /* test auto mipmap generation */
       GLint width, height, i;