The checks that used to be enabled by the flags
UNIV_AHI_DEBUG, UNIV_DDL_DEBUG, UNIV_DEBUG_FILE_ACCESSES
were already enabled in debug builds. So, there is no point
in setting these.

Only UNIV_ZIP_DEBUG is set independently of the debug build.

Allow WITH_INNODB_EXTRA_DEBUG to be set for non-debug builds as well.
Currently it only implies UNIV_ZIP_DEBUG, that is, extra validation
for operations on ROW_FORMAT=COMPRESSED tables.

page_zip_validate_low(): Allow the code to be built on non-debug server.
buf_LRU_block_remove_hashed(): Allow the code to be built without
WITH_INNODB_AHI.