[x265] Issue #544: 'register' storage class specifier deprecated in C++17 (multicoreware/x265)

[puya-mmi]

New issue 544: 'register' storage class specifier deprecated in C++17
https://bitbucket.org/multicoreware/x265/issues/544/register-storage-class-specifier

Puya Daravi:

Compilation fails with clang 10 and std flag set to c\+\+17, giving the following error message while compiling \`md5.cpp\`:

```
error: ISO C++17 does not allow 'register' storage class specifier [-Wregister]
    register uint32_t a, b, c, d;
```

See more details about it in [this stackoverflow answer](https://stackoverflow.com/a/30809775/3847255). Basically the register keyword needs to be removed.