Make verror extern(C) so it can be written in D and called from C++, even though va_list has a different type in dmc and dmd
Refactor macros in arrayop.c
fix Issue 10506 - Purity should not be checked in a mixin statement
fix Issue 10526 - opDispatch with IFTI should not disable UFCS

When opDispatch result is a function template that requires IFTI, it would be kept on `DotTemplateInstanceExp` so `ti->needsTypeInference(sc)` returns TRUE in its semantic().

UFCS dispatch should check that the opDispatch result is really valid or not, by instantiating the function template.
refactor (only) of doswitch()
fix Issue 10519 - Stray-paren in doc-unittest code generates wrong document
fix Issue 7656 - ddoc misinterprets commented parentheses in an example
fix Issue 7715 - DDoc eats $1, $2, $3 etc. inside d_code section
fix Issue 10534 - Addition and subtraction of delegates allowed
fix-up for the improvement of default argument processing
Output ddoc test result to results dir.
Add trait for getting all unit tests of a module.
Add support for UDA's.
Merge pull request #2300 from AndrejMitrovic/Fixup4899

Output ddoc test result to results dir.
Merge pull request #2294 from 9rnsr/fix10534

Issue 10534 - Addition and subtraction of delegates allowed
Merge pull request #2292 from 9rnsr/fix_ufcs

Issue 10526 - opDispatch with IFTI should not disable UFCS
Merge pull request #2289 from 9rnsr/fix10506

Issue 10506 - Purity should not be checked in a mixin statement
Merge pull request #2295 from WalterBright/refactor-doswitch

refactor (only) of doswitch()
optimize sequence of || with BT
Merge pull request #2299 from WalterBright/opt-oror

optimize sequence of ||