pic: move timing structures to RateControlEntry

This saves a bit of memory, since this data only needs to exist when the picture
is being encoded.
pic: move SSIM, PSNR and hash to frame encoder

This data only needs to exist when the picture is being encoded. This changes
the SSIM scores slightly, even though the bitstream and recon does not change,
because it is resetting the SSIM sum and counter each frame.  When these fields
were on the TComPic, they were never cleared.
pic: move m_elapsedCompressTime and m_frameTime to frame encoder

This data only needs to exist when the picture is being encoded
sym: do not return pointer reference from getCU()
TComDataCU: remove hungarian prefixes from CU vars
frameencoder: remove unused bitcounter
frameencoder: replace m_cfg with m_param pointer, use m_top for leftovers
framefilter: replace top pointer with param pointer
TEncSearch: nits
TEncSearch: keep param pointer instead of top encoder pointer

This required cacheing some top encoder fields in TEncSearch
pic: remove unread m_bUsedByCurr

--HG--
extra : amend_source : d4159cf9af4fb411a931faeb63cd54bfeb0e1886
pic: remove unread m_bCheckLTMSB
pic: improve comments

--HG--
extra : amend_source : 06996ac2195f6e4c84d476c019b747ad10ec0337
pic: destroy() no longer needs to be virtual, compress white-space
pic: split picsym allocation from main create function, rename reinit()
pic: nit
pic: keep a pool of TComPicSym, allocate only for encode process

This commit moves the picture freelist to the DPB, it seemed to belong there.
This change reduced memory in a medium encode by more than 40%.
encoder: move EncStats into x265 namespace
frameencoder: make m_ssimCnt an unsigned int
pic: keep the recon TComPicYuv in the pool with the TComPicSym - another 10%