Cleaned up memory allocation for object_entry structs.

Cleaned up memory allocation for object_entry structs.

Although its easy to ask the user to tell us how many objects they
will need, its probably better to dynamically grow the object table
in large units.  But if the user can give us a hint as to roughly
how many objects then we can still use it during startup.

Also stopped printing the SHA1 strings to stdout as no user is
currently making use of that facility.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>