glTexParameteri. Call glGenerateMipmap after every change to the
texture image data.
* clutter/cogl/gles/cogl-gles2-wrapper.h:
* clutter/cogl/gles/cogl-gles2-wrapper.c: Added a wrapper for
glTexParameteri so that it can ignore requests to set
GL_GENERATE_MIPMAP. Added a wrapper for glGenerateMipmap that does
nothing on GLES 1