Enable tpl model for speed 0

Enable tpl model for speed 0

Enable adaptive Lagrangian multiplier for arf in speed 0, AQ mode 0,
and low bit-depth settings. This improves the peak compression
performance:

          avg PSNR       overall PSNR       SSIM
low       -0.462%         -0.535%          -0.358%
mid       -0.780%         -0.857%          -0.868%
hd        -0.914%         -1.017%          -0.471%
720p      -0.624%         -0.671%          -1.553%
nflx2k    -0.764%         -0.784%          -0.908%

The encoding time at speed 0 is slightly changed to be faster or
slower:

city_cif 1000 kbps
78.2 seconds -> 78.1 seconds

bus_cif 1000 kbps
98.6 seconds -> 98.8 seconds.

Change-Id: I18e7337bb61d985cbd3cf29e56439a6cdf675389