Fix 11745: Private unit tests can not be invoked.
Added unittests for issue 11745.
incorrect strlen usage

- causes overflow for empty string
Make Array take the actual type of the stored element
fix Issue 10643 - Refused const array struct field initialized with void

Void initialized non-mutable aggregate members should become instance fields.
fix Issue 11720 - Function-local static variables should cause "already defined in another scope" error
fix Issue 11793 - [ICE] Compiler runs out of memory with trivial program: class with own class member instance
fix Issue 11767 - doubly mixed-in struct "failed semantic analysis"

Inherently this is a mangling issue, which had been hidden since 2a3db5d7afd0c26e8a0ec58ff6fb6a8cd9647de6, and then detected by [the assertion for AST sanity](20fe5e8600498fed322a7d5d8305acb2de852cde).

Each mixed-in symbols are in independent scope, and their mangled names should also be different.
To fix the issue, assign scope-local unique name for each unnamed `TemplateMixin`s, as same as lambdas.
ErrorExp should not inherit from IntegerExp
Remove integer_t
Merge pull request #2972 from MartinNowak/fix11750

incorrect strlen usage
Merge pull request #2964 from 9rnsr/fix10643

Issue 10643 - Refused const array struct field initialized with void
Merge pull request #2963 from Kapps/fix11745

Fix 11745: Private unit tests can not be invoked.
Merge pull request #2947 from 9rnsr/fix11720

Issue 11720 - Function-local static variables should cause "already defined in another scope" error
Merge pull request #3028 from yebblies/integer_t

Remove integer_t
Merge pull request #3021 from yebblies/errorexp

ErrorExp should not inherit from IntegerExp
Merge pull request #2989 from yebblies/arrayptr

[DDMD] Make Array take the actual type of the stored element
Merge pull request #3019 from 9rnsr/fix11767

[REG2.060] Issue 11767 - doubly mixed-in struct "failed semantic analysis"
Merge pull request #3013 from 9rnsr/fix11793

Issue 11793 - [ICE] Compiler runs out of memory with trivial program: class with own class member instance
fix Issue 11818 - Ternary operator not allowed in a value parameter anymore