only used as fallback for now, needs benchmarking.
also notice that some malloc() impls do waste memory to keep track of alignment
and other stuff (check msdn's page on malloc).
* expand test_dynalloc to cover low level aligned alloc funcs. Remove the old
#ifdef EIGEN_VECTORIZE...
* rewrite the logic choosing an aligned alloc, some new stuff:
* malloc() already aligned on freebsd and windows x64 (plus apple already)
* _mm_malloc() used only if EIGEN_VECTORIZE
* posix_memalign: correct detection according to man page (not necessarily
linux specific), don't attempt to declare it if the platform didn't declare it
(there had to be a reason why it didn't declare it, right?)
fd831d5a12