Add ability to only run select numbered tests in ssl-opt.sh

In order to reduce debugging time, allows you to only run interesting
tests (by number) from the commandline.

e.g. the command 'tests/ssl-opt.sh -n 246,258' will only run test 246
and 258 (as per the number in the log file names)
diff --git a/tests/ssl-opt.sh b/tests/ssl-opt.sh
index 1a91f7a..d2cccdb 100755
--- a/tests/ssl-opt.sh
+++ b/tests/ssl-opt.sh
@@ -33,12 +33,15 @@
 FILTER='.*'
 EXCLUDE='^$'
 
+RUN_TEST_NUMBER=''
+
 print_usage() {
     echo "Usage: $0 [options]"
     printf "  -h|--help\tPrint this help.\n"
     printf "  -m|--memcheck\tCheck memory leaks and errors.\n"
     printf "  -f|--filter\tOnly matching tests are executed (default: '$FILTER')\n"
     printf "  -e|--exclude\tMatching tests are excluded (default: '$EXCLUDE')\n"
+    printf "  -n|--number\tExecute only numbered test (comma-separated, e.g. '245,256')\n"
 }
 
 get_options() {
@@ -53,6 +56,9 @@
             -m|--memcheck)
                 MEMCHECK=1
                 ;;
+            -n|--number)
+                shift; RUN_TEST_NUMBER=$1
+                ;;
             -h|--help)
                 print_usage
                 exit 0
@@ -293,6 +299,13 @@
 
     print_name "$NAME"
 
+    # Do we only run numbered tests?
+    if [ "X$RUN_TEST_NUMBER" = "X" ]; then :
+    elif echo ",$RUN_TEST_NUMBER," | grep ",$TESTS," >/dev/null; then :
+    else
+        SKIP_NEXT="YES"
+    fi
+
     # should we skip?
     if [ "X$SKIP_NEXT" = "XYES" ]; then
         SKIP_NEXT="NO"