redis-trib: initial slots allocation strategy, still to improve for better balancing when there are just a few slots to move.

redis-trib: minor refactoring creating a method to load the cluster information starting from a single node

Fixed command table for RESTORE to make it accepting keys only for the right slots when cluster is enabled.

Return errors if a write command is called inside a Lua script after a random command was called. See https://github.com/antirez/redis/issues/95 for more information.

Lua math.random and math.randomseed replaced with our own version based on redisSrand48(). Seed initialized to the same value at every EVAL/EVALSHA call.

libc neutral random function derived from a drand48() implementation added. Will be used to replace Lua's math.random implementation.

rioInitWithFile nad rioInitWithBuffer functions now take a rio structure pointer to avoid copying a structure to return value to the caller.

make sure to return just 1 for rio.c write when the target is a buffer, as we do when the target is a file.

comment on top of the _rio structure modified for correctness as actually fwrite/fread semantics is different in general, but was 0/1 in our old usage before rio.c as we always used 1 as number items, and the actual number of bytes to read as item length.

redis-cli segfaults with single numeric argument greater than zero

fixed a small bug that caused redis-cli to segfault when given single numeric parameter greater that zero.

Spelling fixes.

Corrected typo in documentation for R_Zero, R_PosInf, R_NegInf, R_Nan;

Fixed compilation on Mac/PPC

[issue 620] don't segfault if number of arguments is less than 1