Problem
-------

building with clang and CMAKE_CXX_CFLAGS="-Wdocumetnation" reports
warnings parameters that are documented, but not in the function
declaration.

E.g.:

    /** Gets the desired bits for a given page from a bitmap page.
    @param[in]      page            bitmap page
    @param[in]      page_id         page id whose bits to get
    @param[in]      page_size       page size */
    @param[in]      latch_type      MTR_MEMO_PAGE_X_FIX, MTR_MEMO_BUF_FIX, ...
    @param[in,out]  mtr             mini-transaction holding latch_type on the
    bitmap page
    @param[in]      bit             IBUF_BITMAP_FREE, IBUF_BITMAP_BUFFERED, ...
    @return value of bits */
    UNIV_INLINE
    ulint ibuf_bitmap_page_get_bits_low(const page_t *page,
                                        const page_id_t &page_id,
                                        const page_size_t &page_size,
    #ifdef UNIV_DEBUG
                                        ulint latch_type, mtr_t *mtr,
    #endif /* UNIV_DEBUG */
                                        ulint bit) {
    ...

leads to:

- latch_type
- mtr

be documented even though they aren't in functions prototype if UNIV_DEBUG
isn't defined.

Change
------

- split doc-comment into several parts
- ifdef doc-comment parts in the same way as the function params

RB: 23993