Mangling of /ENTRY depends on DLL imports

[Geod24]

Transferred from: https://issues.dlang.org/show_bug.cgi?id=13984

User @CyberShadow reported (2015-01-15 13:59:20 CET):

///////////// test.d ////////////
extern(System) uint GetVersion();

void main()
{
//    GetVersion();
}
/////////////////////////////////

This program compiles and links fine with the command:

$ dmd -L/ENTRY:_mainCRTStartup test.d 

However, if you uncomment the GetVersion line, linking breaks:

OPTLINK (R) for Win32  Release 8.00.15
Copyright (C) Digital Mars 1989-2013  All rights reserved.
http://www.digitalmars.com/ctg/optlink.html
OPTLINK : Error 180: No Match Found for Export/ENTRY -  : _mainCRTStartup
--- errorlevel 1

To fix linking, the leading underscore needs to be removed from the command line:

$ dmd -L/ENTRY:mainCRTStartup test.d