Change default bucket count in hash_set/hash_map.

Previously these types rehashed to a table of 193 elements
upon construction. But this is non-ideal, first because default
constructors should not allocate unless necessary, and second
because 193 is big and can waste a bunch of memory.

This number had previously been chosen to match GCC's implementation.

git-svn-id: 91177308-0d34-0410-b5e6-96231b3b80d8
6 files changed