Simplify small size class infrastructure.

Program-generate small size class tables for all valid combinations of
LG_TINY_MIN, LG_QUANTUM, and PAGE_SHIFT.  Use the appropriate table to generate
all relevant data structures, and remove the distinction between
tiny/quantum/cacheline/subpage bins.

Remove --enable-dynamic-page-shift.  This option didn't prove useful in
practice, and it prevented optimizations.

Add Tilera architecture support.