fix Issue 10916 - toHash on VariantN not being recognised

Make VariantN.toHash() const nothrow @safe. Assume that `VariantN.type` property is @safe nothrow.
Remove redundant Tuple.opEquals

Today struct type equality `a == b` is expanded to `a.tupleof == b.tupleof`, so opEquals method is unnecessary for `std.tyoecons.Tuple`.
Merge pull request #2303 from 9rnsr/fix_hash

Tweak Tuple and Variant for correct hashing
Merge pull request #2256 from Safety0ff/popbackn

std.algorithm.remove: Fix constraints and change popBack loop to popBackN
Fix issue 12455 [reg]Bad lowercase mapping for 'LATIN CAPITAL LETTER I WITH DOT ABOVE'

Also as part of a fix restores a test case in string.d
to exactly match older behaviour.

Some extended greek is not upper but title case, yet changes on toUpper.
Merge pull request #2296 from Element-126/doc_formatValue_add_example

Add documentation examples for formatValue()
std.json.JSONValue toString is now const
Merge pull request #2292 from markisaa/constToString

Issue 13015 - std.json.JSONValue's toString is now const
Convert std.math.isFinite into a template
Convert std.math.isSubnormal into a template
Add floatTraits.SIGNPOS_BYTE for float
Convert std.math.signbit into a template
Merge pull request #2304 from DmitryOlshansky/issue-12455

[REG]Fix issue 12455 Bad lowercase mapping for 'LATIN CAPITAL LETTER I W...
Convert std.math.copysign into a template
Fixup use of whitespace in places
fix Issue 13056 - [2.066.0-b1] Regression: Error: template std.path.baseName cannot deduce function from argument types !()(DirEntry)
Changed tabs to spaces
Merge pull request #2295 from adamsaka/issue_8370

Issue 8370 - Fix deprecated message during Linux Phobos build.
Merge pull request #2306 from WalterBright/fix13056

fix Issue 13056 - [2.066.0-b1] Regression: Error: template std.path.base...
Fix Issue 13042 - std.net.curl.SMTP doesn't send emails with libcurl-7.34.0 or newer