Allow these hot functions to be inlined. This boosts decode performance by ~10%.

We can avoid using a loop-up table with some shift arithmetics.

Add a opj_t1_dec_clnpass_step_only_if_flag_not_sig_visit() method that
does the job of opj_t1_dec_clnpass_step_only() assuming the conditions
are met. And use it in opj_t1_dec_clnpass(). The compiler generates
more efficient code.

This is essentially used to shift inside the lut_ctxno_zc, which we
can precompute at the beginning of opj_t1_decode_cblk() /
opj_t1_encode_cblk()

Addition flag array such that colflags[1+0] is for state of col=0,row=0..3,
colflags[1+1] for col=1, row=0..3, colflags[1+flags_stride] for col=0,row=4..7, ...
This array avoids too much cache trashing when processing by 4 vertical samples
as done in the various decoding steps.

… (of the non VSC case)

…qc_vsc() with loop unrolling

…oduced in ba1edf6