d: Return the correct value for C++ constructor calls (PR101664)
C++ constructors return void, even though the front-end semantic treats
them as implicitly returning `this'. To handle this correctly, the
object reference is cached and used as the result of the expression.
PR d/101664
gcc/d/ChangeLog:
* expr.cc (ExprVisitor::visit (CallExp *)): Use object expression as
result for C++ constructor calls.
gcc/testsuite/ChangeLog:
* gdc.dg/extern-c++/extern-c++.exp: New.
* gdc.dg/extern-c++/pr101664.d: New test.
* gdc.dg/extern-c++/pr101664_1.cc: New test.