Back reference documentation bug

[codesniffer13]

According to the Boost documentation for Back references
(http://www.boost.org/doc/libs/1_64_0/libs/regex/doc/html/boost_regex/syntax/perl_syntax.html#boost_regex.syntax.perl_syntax.back_references) which seems to be the same at least from 1.37 - 1.64.

Quoting a piece of the documentation:

---

For example the expression:

^(a*).*\1$

Will match the string:

aaabbaaa

But not the string:

aaabba

---

The string which is specified to not match (aaabba), in fact does match. Confirmed on the boost-users mailing list that the engine is correct and the documentation is wrong.