Fix for multiply defined symbols fatal error in polyimport.cpp on win32
Fix for multiply defined symbols fatal error in polyimport.cpp on win32

* the assimp libraries appear to be compiled with zlib support already, so including them again when linking polyimport results in a multiply defined symbols error on visual studio 2010

* removed zlib from the list of link libraries for polyimport on win32 only

* not sure if this needs done on other platforms or not

* verified that polyimport.exe still works after this tweak

* full text of error:

assimp.lib(inflate.obj) : error LNK2005: _inflateInit2_ already defined in zlib.lib(zlib.dll) [Polycode\Build\Tools\Contents\polyimport\polyimport.vcxproj]
assimp.lib(inflate.obj) : error LNK2005: _inflate already defined in zlib.lib(zlib.dll) [Polycode\Build\Tools\Contents\polyimport\polyimport.vcxproj]
assimp.lib(inflate.obj) : error LNK2005: _inflateEnd already defined in zlib.lib(zlib.dll) [Polycode\Build\Tools\Contents\polyimport\polyimport.vcxproj]
Polycode\Build\Tools\Contents\polyimport\Release\polyimport.exe : fatal error LNK1169: one or more multiply defined symbols found [Polycode\Build\Tools\Contents\polyimport\polyimport.vcxproj]

sshaileshk/Polycode,hksonngan/Polycode,carlosmarti/Polycode,Xetlin/Lua,ivansafrin/Polycode,Xetlin/Lua,ivansafrin/Polycode,fodinabor/Polycode,Xetlin/Lua,mcclure/backup-Polycode,carlosmarti/Polycode,carlosmarti/Polycode,GovanifY/Polycode,zeebok/Polycode,zeebok/Polycode,hksonngan/Polycode,sshaileshk/Polycode,GovanifY/Polycode,mcanthony/Polycode,Xetlin/Lua,zeebok/Polycode,cartman300/Polycode,mcanthony/Polycode,fodinabor/Polycode,hksonngan/Polycode,mcanthony/Polycode,sshaileshk/Polycode,thorsummoner/polycode,cartman300/Polycode,thorsummoner/polycode,cartman300/Polycode,fodinabor/Polycode,thorsummoner/polycode,cartman300/Polycode,ivansafrin/Polycode,zeebok/Polycode,mcclure/backup-Polycode,hksonngan/Polycode,fodinabor/Polycode,mcclure/backup-Polycode,sshaileshk/Polycode,ivansafrin/Polycode,mcanthony/Polycode,GovanifY/Polycode,GovanifY/Polycode,thorsummoner/polycode