Related to PR #114423, this PR proposes to unify the naming of the
internal pointer members in `std::vector` and `std::__split_buffer` for
consistency and clarity.
Both `std::vector` and `std::__split_buffer` originally used a
`__compressed_pair<pointer, allocator_type>` member named `__end_cap_`
to store an internal capacity pointer and an allocator. However,
inconsistent naming changes have been made in both classes:
- `std::vector` now uses `__cap_` and `__alloc_` for its internal
pointer and allocator members.
- In contrast, `std::__split_buffer` retains the name `__end_cap_` for
the capacity pointer, along with `__alloc_`.
This inconsistency between the names `__cap_` and `__end_cap_` has
caused confusions (especially to myself when I was working on both
classes). I suggest unifying these names by renaming `__end_cap_` to
`__cap_` in `std::__split_buffer`.
c7df10643b