Optimize conversion to and from boost and std array

[Antony Polukhin]

Those conversions shall not allocate heap memory.

Usage example:

    typedef boost::array<char, 50> buf_type;
    buf_type res = boost::lexical_cast<buf_type>(number_var);
    // use `res.begin()` as a char*

[Antony Polukhin]

(In [79230]) Optimizations for boost and std array (refs #7065)

[Antony Polukhin]

(In [79249]) Documentation update: documented optimizations for boost and std arrays (refs #7065)

[Antony Polukhin]

(In [79266]) Updated documentaion, fixed bug and refactored tests (refs #7065)

[Antony Polukhin]

(In [79297]) Updated documentaion and performance test (now we have info about conversion speed to and from array<>, refs #7065)

[Antony Polukhin]

(In [79363]) Fix tab in documentation (refs #7065)

[Antony Polukhin]

(In [79364]) Merge from trunk (now lexical_cast has optimized conversions to and from array<>, fixes #7065)