Add bit deposit and bit extraction primops

Modern CPUs (on x86, Haswell and newer) have a PDEP instruction for efficient bit deposit and a PEXT instruction for efficient bit extraction. These instructions can be used to implement various data structures.

I propose we add the following set of primops

pdep8#  :: Word#   -> Word#   -> Word#
pdep16# :: Word#   -> Word#   -> Word#
pdep32# :: Word#   -> Word#   -> Word#
pdep64# :: Word64# -> Word64# -> Word64#
pdep#   :: Word#   -> Word#   -> Word#

pext8#  :: Word#   -> Word#   -> Word#
pext16# :: Word#   -> Word#   -> Word#
pext32# :: Word#   -> Word#   -> Word#
pext64# :: Word64# -> Word64# -> Word64#
pext#   :: Word#   -> Word#   -> Word#

Each primop compiles into either a single PDEP/PEXT instruction or a call to some fallback function, implemented in C.

For reference, see the following library that implements FFI wrapper for 32-bit and 64-bit functions for these instructions:

https://github.com/haskell-works/hw-prim-bits