Re: [boost] [foreach][polygon][xpressive][bimap][ptr_container][gil][assign][typeof][msm] PRs for removing executable attribute for files

'assign' and 'ptr_container' seem candidates for community maintenance.

In fact, nobody currently has write access to boostorg/assign and boostorg/ptr_container, which seems a good indication for them being already de-facto "community-maintained", admittedly by a highly select community. So I'm giving the CMT write access to them.