Remove unused NSE library requires

for lib in nselib/*.lua*; do l=${lib#*/}; l=${l%.lua*}; find . -name \
  \*.lua -o -name \*.nse | xargs grep -l "require .$l\>" | xargs grep \
  -c "\<$l\." | grep ':0$' | awk -F: '{print "'$l'", $1}'; done

Did not remove calls to stdnse.silent_require since these can be used to
abort script execution if OpenSSL is not included, even if the script
does not directly call openssl.* (perhaps it uses comm.tryssl instead,
for instance).

Also did not remove require "strict", since that library is special and
modifies the environment.

scripts/http-errors.nse

@@ -37,7 +37,6 @@ categories = {"discovery", "intrusive"}
 author = "George Chatzisofroniou"
 license = "Same as Nmap--See http://nmap.org/book/man-legal.html"
 
-local http = require "http"
 local shortport = require "shortport"
 local stdnse = require "stdnse"
 local table = require "table"