ENH: Use Python allocator for buffer-info allocation
ENH: Use Python allocator for buffer-info allocation

Since small allocations are faster in Python and we combine two
allocations into one, this speeds up buffer creation by 5+%,
not much, but a pretty simple improvements (plus it allows tracemalloc).

There is some deletion here, which should have been part of gh-16389

grlee77/numpy,numpy/numpy,pbrod/numpy,mhvk/numpy,anntzer/numpy,seberg/numpy,madphysicist/numpy,jakirkham/numpy,madphysicist/numpy,seberg/numpy,anntzer/numpy,pbrod/numpy,endolith/numpy,mattip/numpy,numpy/numpy,grlee77/numpy,pdebuyl/numpy,jakirkham/numpy,numpy/numpy,mattip/numpy,charris/numpy,simongibbons/numpy,pbrod/numpy,rgommers/numpy,charris/numpy,pdebuyl/numpy,mhvk/numpy,anntzer/numpy,grlee77/numpy,rgommers/numpy,rgommers/numpy,jakirkham/numpy,pbrod/numpy,grlee77/numpy,madphysicist/numpy,charris/numpy,endolith/numpy,charris/numpy,jakirkham/numpy,simongibbons/numpy,mhvk/numpy,mattip/numpy,mhvk/numpy,endolith/numpy,simongibbons/numpy,seberg/numpy,pdebuyl/numpy,mattip/numpy,jakirkham/numpy,seberg/numpy,simongibbons/numpy,rgommers/numpy,pdebuyl/numpy,pbrod/numpy,grlee77/numpy,anntzer/numpy,mhvk/numpy,madphysicist/numpy,numpy/numpy,madphysicist/numpy,simongibbons/numpy,endolith/numpy