MLOG_ZIP_COMPRESS and MLOG_ZIP_DECOMPRESS with higher-level entry types.
Implement the logging and crash recovery of MLOG_ZIP_PAGE_CREATE.

page_create_zip(): New function for creating a compressed B-tree page.

page_parse_create_zip(): New function for applying a MLOG_ZIP_PAGE_CREATE
redo log record.

btr_page_create(): Remove the prototype.  Add parameters page_zip, level,
prev, and next.

btr0btr.c: Eliminate page_zip_compress() calls where possible.

page_zip_alloc(), page_zip_compress(), page_zip_decompress(),
page_zip_clear_rec(): Remove parameter mtr.

recv_parse_or_apply_log_rec_body(): Handle MLOG_ZIP_PAGE_CREATE.
Add TODO comments for the other added redo log entry types.