btr_validate_level(): Add missing parameter to added buf_page_print() calls.

btr_root_raise_and_insert(): Replace low-level code with page_zip_copy().

page_zip_copy(): New function to copy the data payload of a compressed page,
byte for byte.  The file page header and trailer are not copied, to avoid
overwriting the fields FIL_PAGE_OFFSET, FIL_PAGE_PREV and FIL_PAGE_NEXT.