P0843R14 inplace_vector

Editor notes:
* Unable to apply change to Complexity for "a.swap(b)" in section
  [container.reqmts]; only such \itemdecl is in [container.alloc.reqmts] with different wording.
* Changes to [containers.sequences.general] applied to section
  [sequences.general].
* Unable to apply change to note in "sequence.reqmts.2" - wording does not
  appear to exist.
* Sections named [containers.sequences.inplace.vector.*] renamed to
  [inplace.vector.*].
* [inplace.vector.modifiers] Add commas for clarity.
* [inplace.vector] Minor editorial fixes (e.g. add missing "the").

Author: burblebee