lookahead: call sliceTypeAnalyse when necessary

call sliceTypeAnalyse even when cutree is on or lookaheadDepth or
scenecutThreashold > 0

performs lookahead when lookaheadDepth > 0, activates lookahead for cutree when
b-adapt/bframes =0 and cutree is set , also enables scenecut for bframes = 0
cases. improves psnr/ssim by .5 dB.

--HG--
extra : rebase_source : 367de5cd98a7a4efd13b99ca2bcfe57628756024
rc: avoid issues from zero-residual lookahead blocks, introduce a small bias

--HG--
extra : rebase_source : 1d81da3301636f9788530f748522afdddbade34f
Nalwrite: removed EMULATION_SIZE macro and calculate the emulationSize from Encoded bitstream size

--HG--
branch : stable
extra : source : 356d91e22b250d786ec0560cf5adf6377a202ab9
Merge with stable
encoder: fix the slicetype char table
slicetype: white-space fixes
cli: tweak aq-strength CLI help