Tweak precomputed table size for G
Allocate precomputation arrays on the heap
Remove unused secp256k1_fe_inv_all
Optimize verification: avoid field inverse

Suggested by Greg Maxwell.
Add explanation about how inversion can be avoided
Rewrite field assembly to match the C version
Convert YASM code into inline assembly
Make {mul,sqr}_inner use the same argument order as {mul,sqr}
Rename bench_verify to bench_recovery
Make the benchmarks print out stats