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/sip-enum-users.nse

@@ -7,7 +7,6 @@ local stdnse = require "stdnse"
 local table = require "table"
 local math = require "math"
 local brute = require "brute"
-local creds = require "creds"
 local unpwdb = require "unpwdb"
 
 description = [[