Supplemental change for druntime pull 522.
fix Issue 10498 - `__traits(compiles, ...)` affect program behaviour
fix Issue 10558 - Assertion failure on struct.c:741

A template instance on temlpate argument may not have yet valid `Dsymbol::ident`, so should use `Dsymbol::getIdent()` for hash calculation.
do switch jump tables more often
Merge pull request #2315 from WalterBright/more-jump-tables

do switch jump tables more often
fix Issue 10499 - retro is no longer CTFE-able
Merge pull request #2318 from 9rnsr/fix10499

[REG2.064a] Issue 10499 - retro is no longer CTFE-able
Merge pull request #2314 from 9rnsr/fix10558

[REG2.064a] Issue 10558 - Assertion failure on struct.c:741
Merge pull request #2310 from denis-sh/supplemental-change-for-druntime-pull-522

Supplemental change for druntime pull 522.
Fix issue 10568 CTFE rejects function pointer safety casts

We need to check for function pointer covariance
Merge pull request #2280 from 9rnsr/fix10498

[REG2.061] Issue 10498 - `__traits(compiles, ...)` affect program behaviour
detab test/runnable/closure.d
fix Issue 5911 - Closure destroys the thrown Exception
Merge pull request #2319 from donc/ctfeCastSafety

Fix issue 10568 CTFE rejects function pointer safety casts
Merge pull request #2316 from 9rnsr/fix5911

Issue 5911 - Closure destroys the thrown Exception