Set proctitle: avoid the use of __attribute__((constructor)).

This cased a segfault in some Linux system and was GCC-specific.

Commit modified by @antirez:

1) Stripped away the part to set the proc title via config for now.
2) Handle initialization of setproctitle only when the replacement
   is used.
3) Don't require GCC now that the attribute constructor is no
   longer used.
add a check for aeCreateTimeEvent

1) Add a check for aeCreateTimeEvent in function initServer.
Better panic message for failed time event creation.
Use GCC printf format attribute for redisLog().

This commit also fixes redisLog() statements producing warnings.
Remove too agressive/spamming log in rdb.c.
Remove warning when printing redisBuildId().
A comment in main() clarified.