Dev (#777)

* The new @if directive.

lib/std/core/private/main_stub.c3

@@ -55,7 +55,7 @@ macro int @main_to_void_main_args(#m, int argc, char** argv)
 	return 0;
 }
 
-$if env::os_is_win32():
+module std::core::main_stub @if(env::os_is_win32());
 
 extern fn Char16** _win_command_line_to_argv_w(ushort* cmd_line, int* argc_ptr) @extern("CommandLineToArgvW");
 
@@ -164,5 +164,3 @@ macro int @wmain_to_void_main_args(#m, int argc, Char16** argv)
 	#m(args);
 	return 0;
 }
-
-$endif