Use rtapi_strlcpy() instead of strncpy() to avoid compiler warning

The rtapi_strlcpy() method is already used elsewhere in the file, so this
do not introduce a new dependency.  This fixes the following compiler
warning:

Compiling libnml/rcs/rcs_print.cc
In file included from /usr/include/string.h:495,
                 from libnml/rcs/rcs_print.cc:21:
In function ‘char* strncpy(char*, const char*, size_t)’,
    inlined from ‘int rcs_vprint(const char*, __va_list_tag*, int)’ at libnml/rcs/rcs_print.cc:311:9:
/usr/include/x86_64-linux-gnu/bits/string_fortified.h:106:34: warning: ‘char* __builtin_strncpy(char*, const char*, long unsigned int)’ output may be truncated copying 99 bytes from a string of length 255 [-Wstringop-truncation]
  106 |   return __builtin___strncpy_chk (__dest, __src, __len, __bos (__dest));
      |          ~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Adjust size from 99 to 100, to match strlcpy() sematics and the 100 byte
size of last_error_bufs[][].

Author: petterreinholdtsen

src/libnml/rcs/rcs_print.cc

@@ -308,7 +308,7 @@ int rcs_vprint(const char *_fmt, va_list _args, int save_string)
 	}
 	last_error_buf_filled++;
 	last_error_buf_filled %= 4;
-	strncpy(last_error_bufs[last_error_buf_filled], temp_string, 99);
+	rtapi_strlcpy(last_error_bufs[last_error_buf_filled], temp_string, 100); // 100 or sizeof(temp_string)?
     }
     return (rcs_fputs(temp_string));
 }