Update in chunks

reduces requirements to ForwardRange
Fix std.BigInt bug #9548 plus other new discovered bugs.
Fixed regex loop-back stream to start from the correct position
Merge branch 'master' of https://github.com/D-Programming-Language/phobos
Fixed a bunch of off-by-one errors in the regex code
Remove unnecessary default arguments
Removed unused stream abstraction
Placement of WIKI in std.conv was corrupting docs
[10116] stdio.File.byLine repeats last line forever, readln(ref C[],R) returns bad data

byLine expects readln to return with an empty buffer on end-of-stream,
which readln does not do for wchar and dchar. Also, the readln variant
that takes a terminator range returns incorrect concatenations of
lines because of the same issue. Fixed by setting buffer.length=0 in
readln for this case. Unit test updated to detect this issue.
Merge pull request #1292 from eco/fix-conv-wiki-macro

[trivial] Placement of WIKI ddoc macro in std.conv was corrupting docs
Merge pull request #1295 from M-frankied/byLine-infloop

[10116] stdio.File.byLine repeats last line forever, readln(ref C[],R) r...
[Trivial] fix code style
fix Issue 10122 - `Appender` doesn't work with disabled default construction
Merge pull request #1297 from 9rnsr/fix10122

[REG2.063a] Issue 10122 - `Appender` doesn't work with disabled default construction
fix issue 10167
immutable should be an enum
Merge pull request #1306 from WalterBright/toenum

immutable should be an enum
Merge pull request #1304 from majiang/patch-2

fix issue 10167
Merge pull request #1273 from Diggsey/master

fix issue 9979 - regex back-looper bug
Merge pull request #1231 from Safety0ff/master

Fix std.BigInt bug #9548 plus other new discovered bugs.