Fixed #7748: now upload and register commands don't need to force the encoding anymore : DistributionMetada returns utf8 strings

for the machine ("i386" or "ppc"), even if the executable is
64-bit.

This patchs ensures that the distutils platform architecture
represents the architecture for the executable when running a
64-bit only executable on OSX.

on OSX. Without this patch it wasn't possible after all
to compile extensions on OSX 10.6 with the binary
installer unless the user had installed the (non-default)
10.4u SDK.

Issue #7457: added a read_pkg_file method to distutils.dist.DistributionMetadata so we can read back PKG-INFO files

extensions with msvc9compiler.