[dev][fbcon] make fbcon_flush public
[dev][usb] add 'usb_is_connected'
[lib][pf2font] updates

- fix compile for new module system
- fix framebuffer overflow
- add some useful functions for app/menu
[platform][msm_shared][timer] make mdelay and udelay thread-safe
[platform][msm_shared][mipi_dsi] add delay to trigger_mdp_dsi and fix usage before init
[platform][msm_shared][display*] implement update_start

we can use fbcon_flush now to trigger this.
Also adds a sw double buffer for other devices
[platform][msm_shared] add rule to compile target specific binary
add display_server and menu for a nice fastboot UI