Added clearing timestamp in extra places.
tests: added prepare + append test case
eblob: improved logging in blob_write()
recovery: fixed spelling in docstring
tests: removed unused usage function
XXX
dnet: simplify dnet_time_cmp()
dnet: simplified dnet_id_cmp_str()
dnet: speeded up dnet_id_cmp()
cmake: use libc's memcmp instead of gcc's

On lucid there is 10x boost on using non-gcc's memcmp:
$ gcc -O3 -o test test.c && ./test
Time: 245 ticks (4279 memcmp/tick)
$ gcc -O3 -fno-builtin-memcmp -o test test.c && ./test
Time: 22 ticks (47662 memcmp/tick)

test.c can be found here http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43052