std::ctype<char>::_M_widen_init() is a function authored by Jerry Quinn
<jlquinn@optonline.net>, which was added to libstdc++ with revision 74662 on
Dec 16, 2003 [1].

With permission from Jerry (thankfully received on Oct 9, 2012), we include a
copy of this function in the MADlib repository. The sole intention is to allow
compiling MADlib with recent versions of gcc while still keeping the runtime
dependencies limited to earlier versions of libstdc++. Technical details are
given in src/utils/libstdcxx-compatibility.cpp.

Revision 74662 of the libstdc++-v3 file include/bits/locale_facets.h, where
std::ctype<char>::_M_widen_init() has been copied from, also included the
following notice in the file header [2]:

// As a special exception, you may use this file as part of a free software
// library without restriction. [...]

Links:
[1] http://gcc.gnu.org/viewcvs?diff_format=h&view=revision&revision=74662
[2] http://gcc.gnu.org/viewcvs/trunk/libstdc%2B%2B-v3/include/bits/locale_facets.h?diff_format=h&view=markup&pathrev=74662