bitstream: give bit counter a useful constructor

--HG--
extra : rebase_source : 488fc6c587bab7b975659f80fc6133bc3b8bf136
sei: first step towards simplifying SEI writing

--HG--
extra : rebase_source : 82a76dbc399e66e8e0bff39ad67f2609249af6f9
psyrd: use psyrdcost for PU/TU decision for inter and intra

--HG--
extra : rebase_source : 52caa360182f1d4561a049d0b4bb5c289db7866a
sei: disable HRD with warning when vbv is off

--HG--
extra : rebase_source : 7fe2c750a5806bd69f4ba56e07cc6b13f5eda6f4
quant: Enforce QP range after adding bit-depth offsets

--HG--
extra : rebase_source : 56aa99597a8179d8869a1d4c1b79732e2c18fda0
fix: TOPSKIP refers outside of picture [OUTPUT CHANGE]

--HG--
extra : rebase_source : 0c935d818fdde6f2424195269a1e2f78d52dd7b5
TEncSearch: simplify square block dim logic

this works around a bizarre MSVC warning on those lines.
 '<<' : result of 32-bit shift implicitly converted to 64 bits (was 64-bit shift intended?)

I have no idea why it was implicitly making the result 64bits.

--HG--
extra : amend_source : 27395112c5029b0ccf977c2123a50a29402284e7