minor fix for the skiplist code, resulting in a false positive with valgrind, and in general into a useless small allocation

tests suite initial support for valgrind, fixed the old test suite until the new one is able to target a specific host/port

git hash 00000000 in reelase.h when git is not found enabled again after some shell scripting fix that is now compatible with most shells

buliding of release.h moved into an external script. Avoided recompialtion of redis.c if git sha1 is the same as the previous one