[boost] [leaf] Request to merge bug fix to master for 1.75 release

I'm requesting permission to merge a bug fix by vector-of-bool in LEAF which makes it work correctly with std::system_error: https://github.com/boostorg/leaf/pull/15/commits/efc56d1c703777fea4fef2bd24f... (There is a minor related change on top of this PR, but this bug fix is the important change in behavior. Note that LEAF is a new library in 1.75).