Rewrite HOST[:PORT] extraction routine (less sed, more validation).

The HOST[:PORT] extraction routine was written using several calls to
sed and a bunch of regex post-processing of the bash $@ array.

This replaces that with bash-native array commands, copying $@ into
a $PARAMS array, removing the last element into $TARGET, and then
passing the remainder to openssl s_client.

This adds validation of the TARGET to ensure that it matches what we
expect for a HOST[:PORT]; if a ':' is present, it must be preceded by a
hostname and followed by a port number, otherwise :443 is appended.

The check to ensure that HOST is not an -option is merged into this as
well, since we already test for : at the beginning of the HOST
(indicating that only a port was provided).

Additionally, this now defends against an empty string "" being passed
as the final option, which could occur if a script calling cipherscan
goes awry and starts passing empty values as the target.

top1m may see a slight speed improvement from this commit, as 4 calls to
sed are replaced with native bash functions.

Fixes one "SC2086: Double quote to prevent globbing and word splitting.":

In cipherscan line 1402:
SCLIENTARGS=$(sed -e s,${TEMPTARGET},,<<<"${@}")
                       ^-- SC2086: Double quote to prevent globbing and
                       word splitting.

cipherscan

@@ -1355,27 +1355,21 @@ if (( $# < 1 )); then
     exit 1
 fi
 
-TEMPTARGET=$(sed -e 's/^.* //'<<<"${@}")
-HOST=$(sed -e 's/:.*//'<<<"${TEMPTARGET}")
-PORT=$(sed -e 's/.*://'<<<"${TEMPTARGET}")
-
-# Default to https if no port given
-if [[ "$HOST" = "$PORT" ]]; then
-    PORT=443
-fi
+PARAMS=("$@")
+TARGET=${PARAMS[-1]}
+unset PARAMS[-1]
 
 # Refuse to proceed if the hostname starts with a hyphen, since hostnames can't
 # begin with a hyphen and this likely means we accidentally parsed an option as
 # a hostname.
-if [[ $HOST =~ ^- ]]; then
-    echo "The final argument '$TEMPTARGET' begins with a hyphen '-', which is not a valid HOST[:PORT]." 1>&2
+if [[ -z $TARGET || $TARGET =~ ^[-:] || $TARGET =~ :.*[^0-9] ]]; then
+    echo "The final argument '$TARGET' is not a valid HOST[:PORT]." 1>&2
     exit 1
 fi
+if ! [[ $TARGET =~ : ]]; then
+    TARGET="${TARGET}:443"
+fi
 
-debug "host: $HOST"
-debug "Port: $PORT"
-
-TARGET=$HOST:$PORT
 debug "target: $TARGET"
 
 # test our openssl is usable
@@ -1399,7 +1393,7 @@ if [[ $VERBOSE != 0 ]] ; then
          $OPENSSLBIN ciphers ALL 2>/dev/null
 fi
 
-SCLIENTARGS=$(sed -e s,${TEMPTARGET},,<<<"${@}")
+SCLIENTARGS="${PARAMS[*]}"
 debug "sclientargs: $SCLIENTARGS"