[lmi] Boost.Filesystem v3

[Vadim Zeitlin]

 Hello,

 I'm looking into building LMI using MinGW64 cross-compiler under Cygwin
without using all the identity mounts-related machinery but by simply using
autotools (even though I don't have many hopes that this will become the
official way of building LMI in the future, I still think it would be
useful to at least be able to build it out of the box like this).

 The first stumbling block is building the Boost libraries, notably
Boost.Filesystem. While bjam seems to support cross-compilation in theory,
in practice it fails miserably when trying to cross-compile from Cygwin and
after spending half an hour on this without getting anywhere I decided to
abandon the idea of using bjamp and just compile the file system library
sources directly.

 This is when I discovered that the library has undergone major changes
relatively recently, as stated in the new version documentation[1]:

        Version 3 is a major revision with many new and improved features.
        It may, however, break some user code written for Version 2.

Further, looking at the list of deprecated names[*], I see that LMI code is
clearly affected by these changes as it uses leaf(), branch_path(),
native_file_string() and probably other deprecated/removed functions.

 Of course, I can just ignore this problem for now and use the still
provided v2 and ignore the deprecation warnings. OTOH it looks like LMI
would need to start using v3 sooner or later and, at the personal level,
I'd like to look at the new changes as they seem to go in the right
direction to me and so I'd like to learn more about them, so I wanted to
ask if you'd be interested in me looking at the new API and producing a
patch allowing LMI to compile with it (such patch could either replace the
v2 API with the new ones or use simple "#if BOOST_FILESYSTEM_VERSION == 3"
checks to allow compiling with both the old and the new versions depending
on your preference).

 What do you think?
VZ

[1] http://www.boost.org/doc/libs/1_46_1/libs/filesystem/v3/doc/index.htm
[2] http://www.boost.org/doc/libs/1_46_1/libs/filesystem/v3/doc/deprecated.html