LDC / BetterC / _d_run_main

[Richard]

Hi,
I've been trying to see if I can get an mbed project to work with 
Dlang
basically compiling D code for use on a Cortex-M Proccessor
So far I've been using the latest release of LDC with the 
-BetterC Flag
 From what I can gather, normally without -BetterC it works like 
this:

   * main() - C main generated by the compiler
   * _d_run_main - called by C main to setup the runtime
   * _Dmain - main function in D land, is called by _d_run_main

With -BetterC enabled, it instead works like this

   * main() - C main generated by the compiler
   * _d_run_main - needs to be written by the user since there's 
no runtime
   * _Dmain - main function in D land

so basically I need to write my own basic _d_run_main to call 
_Dmain.
Code in github does something like this typically
```
private alias extern(C) int function(char[][] args) MainFunc;
private extern (C) int _d_run_main(int argc, char** argv, 
MainFunc mainFunc)
{
     return mainFunc(null);
}
```

However the LDC compiler doesn't like this as it expects the 
mainFunc parameter to be a void pointer
so I tried this instead
```
extern (C) int _d_run_main(int argc, char **argv, void* mainFunc) 
{
     MainFuncType mFunc = cast(MainFuncType) mainFunc;
     return mFunc(null);
}
```

but nope that didn't seem to work ether, compiles okay but the 
code in main() (D space) isn't called
I'd imagine this should be a simple thing, anyone got any ideas?