This allows to override the mangling of a type in an alias declaration as follows:
pragma(mangle, "foo") alias foo = int;
static assert(foo.mangleof == "foo");
static assert(int.mangleof == "i");
Overriding the mangling of a type in an alias allows for more generic solution to get the correct mangling of `c_long/c_ulong` for C++ functions. With the current solution the compiler is looking for a struct with the name `__c_long/__c_ulong` and special cases the mangling for that particular struct. Since D doesn't have implicit conversions to structs one are also forced cast/explicitly construct a `__c_long` struct when calling a function which uses the `__c_long` type as a parameter. With an alias that's not necessary anymore.