MEM_PROC TEXTSTR MEM_API StrCpyEx(TEXTSTR s1, CTEXTSTR s2, size_t n);
copy S2 to S1, with a maximum of N characters.
The last byte of S1 will always be a 'nul'. If S2 was longer than S1, then it will be truncated to fit within S1. Perferred method over this is SaveText or StrDup.