High-level feature map: `vecLib` gaps

[luke-kiernan]

I decided to do an inventory of vecLib for gaps. Here's symbols that aren't covered by LibBLASTrampoline.jl nor this library, that could be worth wrapping:

1. A couple array functions in libvMisc: vvcbrt{f}, vvnextafter{f}, vvpows{f}, vvremainder{f}. Easy to add.
2. The remainder of libSparse: iirc we're missing subfactor, preconditioning, iterative methods, and rank 2 updates.
3. A handful of ATLAS functions in libBLAS: catlas_caxpby (C = aX + bY, no equivalent in BLAS according to AI) and the like. More involved.
4. Libraries with no wrappers at all here: libQuadrature, libSparseBLAS, libBigNum. Notes: libBigNum.dylib is just a broken symbolic link. Its symbols are in libvMisc.dylib instead. libSparseBLAS looks less wrappable than libSparse: more low-level, opaque internal representation.

I didn't check libBNNS or libvDSP.