Introduced the Build ID in INFO and --version output.

The idea is to be able to identify a build in a unique way, so for
instance after a bug report we can recognize that the build is the one
of a popular Linux distribution and perform the debugging in the same
environment.

src/redis.h

@@ -1046,6 +1046,7 @@ void scriptingInit(void);
 /* Git SHA1 */
 char *redisGitSHA1(void);
 char *redisGitDirty(void);
+uint64_t redisBuildId(void);
 
 /* Commands prototypes */
 void authCommand(redisClient *c);