Our public headers suppress MSVC warnings about “less secure” functions

[gilles-peskine-arm]

Since PolarSSL, our config header contains

#if defined(_MSC_VER) && !defined(_CRT_SECURE_NO_DEPRECATE)
#define _CRT_SECURE_NO_DEPRECATE 1
#endif

We do this because when we build the library, we want to be able to use some functions that MSVC doesn't like, such as fopen(). But we shouldn't impose this on third-party applications. Depending on whether you include system headers before or after an Mbed TLS or TF-PSA-Crypto header, you will or will not get a warning if you use a function that MSVC considers deprecated.

We should only define _CRT_SECURE_NO_DEPRECATE when building our own code, i.e. in common.h in 3.6 and in *_platform_requirements.h in 1.1/4.1.

[irwir]

#define _CRT_SECURE_NO_DEPRECATE 1

A value should not be here, just #define _CRT_SECURE_NO_DEPRECATE.
The warning might be disabled in the library project and thus excluded from headers.