With this commit options not explicitly rewritten by CONFIG REWRITE are
not touched at all. These include new options that may not have support
for REWRITE, and other special cases like rename-command and include.

At the end of the file, CONFIG REWRITE adds a comment line that:

    # Generated by CONFIG REWRITE

Followed by the additional config options required. However this was
added again and again at every rewrite in praticular conditions (when a
given set of options change in a given time during the time).

Now if it was alrady encountered, it is not added a second time.

This is especially important for Sentinel that rewrites the config at
every state change.

This fixes issue #1094.

time_t is always 64bit on recent versions of NetBSD.

This way just after the CONFIG SET enabling the min-slaves feature it is
possible to write to the database without delays.

This feature allows the user to specify the minimum number of
connected replicas having a lag less or equal than the specified
amount of seconds for writes to be accepted.

Should be "continue" and was "return".

This fixes issue #1110

Also the logfile option was modified to always have an explicit value
and to log to stdout when an empty string is used as log file.

Previously there was special handling of the string "stdout" that set
the logfile to NULL, this always required some special handling.

This is just to make the code exactly like the above instance used for
requirepass. No actual change nor the original code violated the Redis
coding style.

Fix bug in configGetCommand function: get correct masterauth value.

Usually this does not happens since we trim for " \t\r\n", but if there
are other chars that return true with isspace(), we may end with an
empty argv. Better to handle the condition in an explicit way.