[Issue 19271] New: C++ exception handling does not work on OSX

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=19271

          Issue ID: 19271
           Summary: C++ exception handling does not work on OSX
           Product: D
           Version: D2
          Hardware: All
                OS: Mac OS X
            Status: NEW
          Severity: major
          Priority: P1
         Component: druntime
          Assignee: nobody at puremagic.com
          Reporter: pro.mathias.lang at gmail.com

The typeinfo stuff and exception types (core.stdcpp.{typeinfo,exception} are
not defined on OSX, but are on Windows and CRuntime_Glibc.

Reproduce with:
```
import core.stdcpp.exception;
void main () { exception e; }
```

And get: `x.d(2): Error: undefined identifier exception, did you mean class
Exception?`

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