Bring some accuracy on the fps counter:

Bring some accuracy on the fps counter:
- Get the time with gettime(GETTIME_REALTIME) because for some reason the vars time and frametime are not accurate (frametime and (time - time of previous frame) are always > 0.1) and because otherwise fps depend on slowmo value
- Fix inaccurate fps at low hud_panel_engineinfo_framecounter_time values and default this cvar to 0.1 instead of 1 for both fast update and good reading