Investigate liblzf segfaults

[danielealbano]

When generating the RDB snapshots, if strings are compressed with liblzf using the LZF algorithm, cachegrand crashes with a segfault.

The crash needs to be investigated.

[danielealbano]

liblzf uses an obscene amount of stack to compress the data, about 1mb, meanwhile cachegrand uses about 40kb for its own fibers.

There are two options:

• replace liblzf with something that doesn't abuse the stack in that way
• run the snapshotting via a special fiber using a different stacksize, but this would prevent the normal fibers to snapshot a value that is being replaced but supposed to be snapshotted.

Further investigation is required

[danielealbano]

Will implement the second option as it's the ones the makes most sense