Fix for [-Wtype-limits] compiler warning on 32bits platforms in Sodium extension

[Girgias]

To achieve this we use no-op operations which force the conversion to unsigned long long

This was flagged while working on #5151, just putting this up as a PR as a sanity check and see if someone else has a better idea how to go about it.

[nikic]

I would prefer to wrap this in a #if SIZEOF_SIZE_T != 4 block. Adding the dummy multiplication seems prone to break with newer compiler versions.

[cmb69]

This patch looks bogus, since the left hand side of the expression is already unsigned long long. The actual "problem" here is that msg_len is declared as size_t which has 32bits on x86, but the right hand side of the comparison is way larger. See Nikita's comment above for a possible solution.

[cmb69]

Forgot: this should also go into https://github.com/jedisct1/libsodium-php, or maybe only to there (and later back-ported).

[Girgias]

I would prefer to wrap this in a #if SIZEOF_SIZE_T != 4 block. Adding the dummy multiplication seems prone to break with newer compiler versions.

That seems better in all aspects.

Forgot: this should also go into https://github.com/jedisct1/libsodium-php, or maybe only to there (and later back-ported).

Will send a PR upstream then

[Girgias]

This has been declined upstream, will just add a specific compiler flag to this extension to suppress those warnings.