This adds MSVC versions of getenv() and friends. These take UTF-8
arguments and return UTF-8 values, but use the UNICODE versions
of the CRT routines. This avoids the need to write to __environ
(which is only visible if you statically link to the CRT). This
also avoids the CP_ACP conversions performed inside the CRT.
It also avoids various memory leaks and problems.
Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>