remove intentional leak in win32/win32.c ansify_path

The leak for was workaround for a bug (feature?) of Borland RTL where
putenv kept the passed in pointer, see commit 3e5d884e5e .
Borland was removed so this goes too. Leak found with Dr Memory.
msvcrt.dll from WinXP SP3 does not leak on a call to putenv, static linked
CRT from VC6 was confirmed to leak.