treewide: "require" + "use" cleanup and docs

There's a bunch of leftover "require" and "use" statements we no
longer need and can get rid of, along with some excessive
imports via "use".

IO::Handle usage isn't always obvious, so add comments
describing why a package loads it.  Along the same lines,
document the tmpdir support as the reason we depend on
File::Temp 0.19, even though every Perl 5.10.1+ user has it.

While we're at it, favor "use" over "require", since it it gives
us extra compile-time checking.

1 files changed, 2 insertions, 1 deletions

diff --git a/lib/PublicInbox/HTTP.pm b/lib/PublicInbox/HTTP.pm
index d2f04ba5..1346901a 100644
--- a/lib/PublicInbox/HTTP.pm
+++ b/lib/PublicInbox/HTTP.pm
@@ -15,9 +15,10 @@ use fields qw(httpd env input_left remote_addr remote_port forward alive);
 use bytes (); # only for bytes::length
 use Fcntl qw(:seek);
 use Plack::HTTPParser qw(parse_http_request); # XS or pure Perl
+use Plack::Util;
 use HTTP::Status qw(status_message);
 use HTTP::Date qw(time2str);
-use IO::Handle;
+use IO::Handle; # ->write
 use PublicInbox::DS qw(msg_more);
 use PublicInbox::Syscall qw(EPOLLIN EPOLLONESHOT);
 use PublicInbox::Tmpfile;