C++ Builder and mem.h ambiguity

It's very weird issue, but currently we have ambiguity between "mem.h" from ZSTD and from Embarcadero RAD Studio (C++ Builder which is actually based on clang) See: https://docwiki.embarcadero.com/RADStudio/Alexandria/en/Memset,_wmemset
Currently it is not possible to compile ZSTD with RAD Studio unless rename "mem.h" to, say, "zstd_mem.h"

All other your programs like LZ4 and XXHASH have no compile issues with C++ Builder.