Refurbish memory management from Boost.SIMD SDK

This patch reimplement a large part of the memory management system of Boost.SIMD.

It includes : 

 - [BREAKING CHANGE] - boost::simd::memory as a namespace is deprecated
 - [BREAKING CHANGE] - boost::simd::byte is deprecated
 - [BREAKING CHANGE] - load and store functions and their aligned versions were renamed to follow the {}/{aligned_} pattern of the rest of the library. So load and store perform on unaligned memory whiel aligned_load/store perform on aligned memory only.
 - [BREAKING CHANGE] memory is now a part of boost.sdk and a subset of files have been moved aroudn to accomodate a cleaner, more direct include path

 - [FIX] Fix #349 by revamping relationship between load(a0) and laod(a0,a1) and other similar functions
 - [FIX] Fix #339 by correcting code for reallcoate and introducign reuse as a non-copying reallocate
 - [Fix] Fix #454 by SFINAE-ign out improper combo of type and pointer type in some generic (mostly Altivec) load/store implementation
 - [FIX] Fix #418 by providign a bench a la memcpy of memory load/store functions
 - [FIX] Fix #350 by making insert/extract prototype more homogeneous

 - [NEW] Added new macro to build stack based aligned buffer
 - [NEW] Improved interface for memory allcoation by allowing allcoator based memory amangement at function level, low level C style allcoation function
 - [NEW] Refurbished familly of SIDM rnage and iterator by explicitly havign different, properly named iterator and range for aligned and unaligned SIMD iterators, realigned range, shifting widnow iterator and non-temporal store iterators
 - [NEW] Added a slide<N> function that generically wraps vec_sld like behavior
 - [NEW] Added more optiosn for overloadign new/delete with alginemtn constraints
 - [NEW] Large amount of doc have been added to memory module