[h323plus] Porting Project for Visual Studio 10 Beta

[Marcos Fábio Jardini]

Hello people

   Call me crazy but since I'm testing new Visual Studio 10, the
awesome C++0x lambda functions, rvalue reference and Parallel Pattern
Library, I take the opportunity to see how PTLib and H323plus
solutions compile on VS10.

   The nice news is now Microsoft will separate the compilation from
IDE, now solutions/projects are more self-contained for use with
MSBuild system (wich comes with Windows SDK), the 1st modification is
to use the install-path env-var in the project file itself, like the
*NIX flavors of H323plus, ie, the old "Tools->Oprtions->Projects and
Solutions-> VC++ Directories" are now in "Project->Properties".

    Resuming, there is no more needed to hardcode H323Plus and PTLib
paths on IDE, paths are now Project properties :)

    The 'configure' files updated to WindowsSDK v7.0A. Because VS path
changing from beta 1 to beta 2 I'll wait until RC or RTM to write back
the correct 'configure' file.

    The basic ptlib compiles fine.

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