Documentation update: documented optimizations for boost and std arrays (refs #7065)

[SVN r79249]

doc/lexical_cast.qbk

@@ -70,6 +70,15 @@ The following example uses numeric data in a string expression:
         log_message("Error " + boost::lexical_cast<std::string>(yoko) + ": " + strerror(yoko));
     }
 ``
+Following example converts some number and puts it to file:
+``
+    int i;
+    FILE* file;
+    ...
+    typedef boost::array<char, 50> buf_t;	// You can use std::array if your compiler supports it
+    buf_t buffer = boost::lexical_cast<buf_t>(i); // No dynamic memory allocation
+    puts(buffer.begin(), file);
+``
 [endsect]
 
 [section Synopsis]
@@ -239,12 +248,20 @@ limitation of compiler options that you use.
 , `"-inf"` (case insensitive) strings to get NaN and Inf values. `boost::lexical_cast<string>` outputs `"-nan"`, `"nan"`,
 `"inf"`, `"-inf"` strings, when has NaN or Inf input values.
 
+[pre
+]
+
 * [*Question:]    What is the fastest way to convert a non zero terminated string or a substring using `boost::lexical_cast`?
   * [*Answer:]      Use `boost::iterator_range` for conversion. For example, if you whant to convert to `int` two characters from a string `str`, you shall write `lexacal_cast<int>(make_iterator_range(str.c_str(), str.c_str() + 2));`.
 
 [endsect]
 
 [section Changes]
+
+* [*boost 1.51.0 :]
+
+    * Better performance, less memory usage for `boost::array<character_type, N>` and `std::array<character_type, N>` conversions.
+
 * [*boost 1.50.0 :]
 
     * `boost::bad_lexical_cast` exception is now globaly visible and can be catched even if code is compiled with -fvisibility=hidden.