Warnings on MSVC 2005

[e4lam]

I've found that when using Boost on Microsoft Visual Studio C++ 2005, I get warning C4103 when 
including any boost header which end up including:

abi_{prefix,suffix}.hpp
(eg. iostreams/filter/zlib.hpp)

or which manually performs a 

#include BOOST_ABI_{PREFIX,SUFFIX}
(eg. regex/v4/regex_traits_defaults.hpp).

An explanation for the warning can be found here:
http://windowssdk.msdn.microsoft.com/en-us/library/t4d0762d.aspx

What is happening is that config/abi/msvc_{prefix,suffix}.hpp performs "#pragma 
pack(push,8)" (in msvc_prefix.hpp) and then performs a "#pragma pack(pop)" (in msvc_suffix.hpp). This leads the compiler to think that the packing alignment has erroneously changed, generating unnecessary warnings.