Recommend using portable std.ascii.newline for line terminator

Also document 'lines' constructor.
Note that readln() cannot support string terminators
fix property enforcement
Don't use std.ascii.newline with text mode
Merge pull request #2390 from 9rnsr/enforceProp

fix property enforcement
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
std.getopt: Remove opinionated comment regarding option bundling

The behavior is standard in UNIX programs. Although it wouldn't make sense
to change the default at this point, D documentation is not a good place
for criticizing established standards.
Merge pull request #2398 from CyberShadow/getopt-bundling-doc

std.getopt: Remove opinionated comment regarding option bundling
Replace use of T.min to determine signedness with std.traits.isUnsigned.
Merge pull request #2386 from MetaLang/variant-remove-float-min

Fix Issue 13230: std.variant.Variant Uses Deprecated .min Property in opArithmetic When T is a Floating Point Type
Eliminate bad use of alias
Merge pull request #2399 from Hackerpilot/remove-bogus-alias-use

Eliminate bad use of alias
Flush stdout after writeln (fixes issue #13241)
Only flush for DMC stdio.