fil_page_decompress(): Replaces fil_decompress_page().
Allow the caller detect errors. Remove
duplicated code. Use the "safe" instead of "fast" variants of
decompression routines.

fil_page_compress(): Replaces fil_compress_page().
The length of the input buffer always was srv_page_size (innodb_page_size).
Remove printouts, and remove the fil_space_t* parameter.

buf_tmp_buffer_t::reserved: Make private; the accessors acquire()
and release() will use atomic memory access.

buf_pool_reserve_tmp_slot(): Make static. Remove the second parameter.
Do not acquire any mutex. Remove the allocation of the buffers.

buf_tmp_reserve_crypt_buf(), buf_tmp_reserve_compression_buf():
Refactored away from buf_pool_reserve_tmp_slot().

buf_page_decrypt_after_read(): Make static, and simplify the logic.
Use the encryption buffer also for decompressing.

buf_page_io_complete(), buf_dblwr_process(): Check more failures.

fil_space_encrypt(): Simplify the debug checks.

fil_space_t::printed_compression_failure: Remove.

fil_get_compression_alg_name(): Remove.

fil_iterate(): Allocate a buffer for compression and decompression
only once, instead of allocating and freeing it for every page
that uses compression, during IMPORT TABLESPACE. Also, validate the
page checksum before decryption, and reduce the scope of some variables.

fil_page_is_index_page(), fil_page_is_lzo_compressed(): Remove (unused).

AbstractCallback::operator()(): Remove the parameter 'offset'.
The check for it in FetchIndexRootPages::operator() was basically
redundant and dead code since the previous refactoring.