std.process: memory allocation with malloc in execv_

[kdevel]

Why is the memory in `execv_` in `std.process` allocated with 
`malloc` (`core.stdc.stdlib.malloc`) and why is this memory not 
registered with the GC? It seems to be responsible for the memory 
corruption in [1].

```
diff --git a/process.d b/process.d
index 3eaa283..cea45a9 100644
--- a/process.d
+++ b/process.d
@@ -4295,7 +4295,9 @@ private int execvp_(in string pathname, in 
string[] argv)
      import std.exception : enforce;
      auto argv_ = 
cast(const(char)**)core.stdc.stdlib.malloc((char*).sizeof * (1 + 
argv.length));
      enforce!OutOfMemoryError(argv_ !is null, "Out of memory in 
std.process.");
-    scope(exit) core.stdc.stdlib.free(argv_);
+    import core.memory;
+    GC.addRange (argv_, (char *).sizeof * (1 + argv.length));
+    scope(exit) { GC.removeRange (argv_); 
core.stdc.stdlib.free(argv_); }

      toAStringz(argv, argv_);
```

[1] https://issues.dlang.org/show_bug.cgi?id=23654
     Issue 23654 - execv_: toAStringz: memory corruption