Add additional option read_always to exported options
Remove ported and unused settings from Glide64mk2.ini

All used non-special (which would be overwritten by games) are currently
exported by the config API. The only missing ones for the special configu
options are

 * alt_tex_size
 * use_sts1_only
 * force_calc_sphere
 * correct_viewport
 * increase_texrect_edge
 * decrease_fillrect_edge
 * texture_correction
 * pal230
 * stipple_mode
 * stipple_pattern
 * force_microcheck
 * force_quad3d
 * clip_zmin
 * clip_zmax
 * fast_crc
 * adjust_aspect
 * zmode_compare_less
 * old_style_adither
 * n64_z_scale
 * optimize_texrect
 * ignore_aux_copy
 * hires_buf_clear
 * fb_read_alpha
 * useless_is_useless
 * fb_crc_mode
 * filtering
 * fog
 * buff_clear
 * swapmode
 * aspect
 * lodmode
 * fb_smart
 * fb_hires
 * read_back_to_screen
 * detect_cpu_write
 * fb_get_info
 * fb_render
Add additional option aspectmode to exported options

This options are now editable by the user and frontends. Possible values are:

0 = Force 4:3 (default)
1 = Force 16:9
2 = Stretch
3 = Original