log2: floor_log2
bit_spinlock: dummy_bit_spinlock

For radix_array users that don't need locking.
umalloc: Brand new user-space allocator

This one should be much faster and smarter (at least, it's a bit
faster for Metis on Linux at 80 cores).  It's still very per-core, but
it doesn't depend on scanning free lists to find fits or to perform
merging.
stdinc: Move errnos into stdinc and delete include/errno.h

include/errno.h messes some things up when building Metis for Linux.
metis: Fix Linux build
metis: Unconditionally enable debug info
metis: Only run 64K and 8M points
metis: Use new umalloc in Linux build
metis: Even better ben runner
umalloc: Comment overall design and more internal functions