Replace misused xr_sprintf -> vsnprintf.

Author: nitrocaster

src/xrCore/xrstring.h

@@ -96,7 +96,7 @@ class shared_str
         string4096 buf;
         va_list p;
         va_start(p, format);
-        int vs_sz = xr_sprintf(buf, sizeof(buf) - 1, format, p);
+        int vs_sz = vsnprintf(buf, sizeof(buf) - 1, format, p);
         buf[sizeof(buf) - 1] = 0;
         va_end(p);
         if (vs_sz) _set(buf);