Redefine getpid() -> _getpid() only for MSVC
Redefine getpid() -> _getpid() only for MSVC

This was introduced in 814b5133e for MSVC. C++Builder doesn't need it.

Reviewed-by: Paul Dale <ddec78389666b4f7c9b4d110380c848489a3e4aa@openssl.org>
Reviewed-by: Matthias St. Pierre <1910231d24f125aceac7850dc92279eee8d52323@ncp-e.com>
Reviewed-by: Dmitry Belyavskiy <38c64d6e24766247aad56af3a6ddb0056ad36a44@gmail.com>
(Merged from https://github.com/openssl/openssl/pull/16192)

openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl