Windows: UTF-8 opt-in for command-line arguments and console input.

User can make Windows openssl.exe to treat command-line arguments
and console input as UTF-8 By setting OPENSSL_WIN32_UTF8 environment
variable (to any value). This is likely to be required for data
interchangeability with other OSes and PKCS#12 containers generated
with Windows CryptoAPI.

Reviewed-by: Richard Levitte <levitte@openssl.org>