not even when restoring an uncompressed page after a compression failure.

btr_page_reorganize_low(): On compression failure, do not restore
those page header fields that should not be affected by the
reorganization.  Instead, compare the fields.

page_zip_decompress(): Add the parameter ibool all, for copying all
page header fields.  Pass the parameter all=TRUE on block read
completion, redo log application, and page_zip_validate(); pass
all=FALSE in all other cases.

page_zip_reorganize(): Do not restore the uncompressed page on
failure.  It will be restored (to pre-modification state) by the
caller anyway.

rb://167, Issue #346