If a newline has a backslash in front of it, then str_rd replaces it
with a space. However, the newline was in the original config file,
so the line number must still be incremented.
Previously, it only pretended to rewrite the configuration file, so it
set or cleared OPT_MUST_SAVE but never changed or output any options.
Now, it actually sets the options when ELinks is loading the
configuration file. Also, when ELinks is rewriting the configuration
file, it now compares the values in the included file to the current
values of the options, and sets or clears OPT_MUST_SAVE accordingly.
So if ELinks is rewriting a configuration file that contains a "set"
command for a negated alias, then it properly writes the value of the
alias, rather than the value of the underlying option.
That is, let the setter function of the underlying option store the
negated value. Previously, redir_set used to tweak the value of the
option after it has already called the underlying setter.
