D lang compilers have an option -release (or similar) which turns off
asserts, contracts, and other runtime type checking. This patch wires
that up to the b_ndebug flag.
Fixes#7082
* Add a new compiler object method: has_members
Identical to 'cc.has_member', except that this takes multiple members
and all of them must exist else it returns false.
This is useful when you want to verify that a structure has all of
a given set of fields. Individually checking each member is horrifying.
* Fix typo in exceptions for has_member(s)