win32: update portage

- fix the building of vle.dll using flag VLE_DLL.
- remove static vle library (remove BUILD_SHARED_LIBS option).
- build a libgvle.dll fo win32.
- template: use static boost libs.
- template: add cmake macro for test building.
- Define the cmake FindPackage scripts : VLE, VLE_DEPS, GVLE, GVLE_DEPS.
- Modify gvle.pc to find libgvle for win32.
win32: split gvle.exe and libgvle.dll

To simplify the CMakeLists.txt scripts, we build a shared library
libgvle.{dll|so} on both POSIX and WIN32.

We move the program gvle.exe into src/apps/gvle directory. gvle.exe use
libgvle.{dll.so} at runtime.
win32: fixing Gtk problem with dll and application

With mingw32, gvle.exe (only depends to libgvle.dll and libvle.dll), the
Gtk::Window is not displayed if the Gtk::Main loop is in gvle.exe and the GVLE
class is in the libgvle.dll. This seems to be a bug in Gtk since with have no
problem to run gvle.exe statically linked with libgvle. To fix the problem, we
introduce the static start function in libgvle.dll which wraps the Gtk::Main
loop into libgvle.dll. Now the gvle.exe application have only a call to this
function.
win32: build static libraries for vle and gvle

To achieve a better compatibility with porting linux and windows
application, we generate static and shared libraries for vle and gvle.
vle: removing the fatal error with missing deps

On Debian/Stable, several pkg-config files are missing. We need to
remove the fatal error.
vle: updating source code to libarchive 2
win32: fix PathWin32::getTempFile

Fix the confusion between the directory name and the filename
(Closes #55)
utils: use Boost::Asio rather than libcurl

DownloadManager now relies on Boost::Asio to perform a HTTP GET request
for downloading files (Closes #56).
vle: remove useless dependencies

The Boost::Asio does not depend to openssl libssh2 libssl libidn gnutls
hogweed libcrypto nettle. So we remove them.
vle: restore the libxml2 initialization

We restore the xmlInitParser() in vle::Init constructor.
utils: add unit test for DownloadManager

We add a test in DownloadManager. This unit test check the download of
the vle-1.0.0.dtd from www.vle-project.org server. We use BOOST_CHECK
instead of BOOST_REQUIRE.
utils: export DownloadManager symbols

To use DownloadManager class from external prorgam (as unit test), we
need to export the symbols.
utils: fix coding style in DownloadManager

Fix several coding style errors.