Recommend using portable std.ascii.newline for line terminator

Also document 'lines' constructor.
Note that readln() cannot support string terminators
Don't use std.ascii.newline with text mode
std.bitmanip BitArray refactor and various fixes
Merge pull request #2249 from Safety0ff/bitarrayrefact

std.bitmanip BitArray refactor
Merge pull request #2364 from ntrel/stdio-newline

[docs] Recommend std.ascii.newline for portable line terminator in std.stdio