owl_util_file_deleteline: Prevent FD leak in error paths

Found by Coverity Scan service.

Signed-off-by: Anders Kaseorg <andersk@mit.edu>
owl_function_debugmsg: Be sure to match va_start with va_end

Found by Coverity Scan service.

Signed-off-by: Anders Kaseorg <andersk@mit.edu>
owl_zephyr_load{subs,loginsubs}: Eliminate useless stat call

Placates Coverity Scan service, which detects a TOCTOU race between
stat and fopen.  This race was in fact hiding an unlikely memory leak.

Signed-off-by: Anders Kaseorg <andersk@mit.edu>
owl_variable_bool_get_tostring_default: Remove dead <invalid> case

bool is 0 or 1.  Found by Coverity Scan service.

Signed-off-by: Anders Kaseorg <andersk@mit.edu>
Give a hint about package provenance.

Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>
Fix quoting conventions for Twitter commands.

Two bugs here:

1. The documentation incorrectly implies that arguments can be
omitted, when really the argument parser is much dumber than that.
If there are two optional arguments, you can't omit the first one
and give the second one; that's ambiguous.

2. There is a codepath for replycmd when status_id is not set
(this should be impossible) which passed wrong arguments.

Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>
Implement Twitter at-reply prefill semantics.

Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>
Link to status instead of user page.

Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>