Fixing up make html target

Add types of files that genhtml (the program that generates html files
from .gcno/.gcda files, included in lcov) should ignore, such as .yy and
.ll files.

testing/coverage/lcov_html.sh

@@ -0,0 +1,61 @@
+#!/usr/bin/env bash
+#
+# On a Bro build configured with --enable-coverage, this script
+# produces a code coverage report in HTML format after Bro has been invoked. The
+# intended application of this script is after the btest testsuite has run.
+
+# This depends on lcov to run.
+
+function die {
+	echo "$@"
+	exit 1
+}
+function finish {
+	rm -rf "$TMP"
+}
+function verify-run {
+	if bash -c "$1" > /dev/null 2>&1; then
+		echo ${2:-"ok"}
+	else
+		die ${3:-"error, abort"}
+	fi
+}
+trap finish EXIT 
+
+COVERAGE_FILE="./$TMP/coverage.info"
+COVERAGE_HTML_DIR="${1:-"coverage-html"}"
+REMOVE_TARGETS="*.yy *.ll *.y *.l"
+
+# 1. Move to base dir, create tmp dir
+cd ../../; 
+TMP=".tmp.$$"
+mkdir "$TMP"
+
+# 2. Check for .gcno and .gcda file presence
+echo -n "Checking for coverage files... "
+for pat in gcda gcno; do
+    if [ -z "$(find "$BASE" -name "*.$pat" 2>/dev/null)" ]; then
+        echo "no .$pat files, nothing to do"
+	exit 0
+    fi
+done
+echo "ok"
+
+# 3. If lcov does not exist, abort process. 
+echo -n "Checking for lcov... "
+verify-run "which lcov" \
+	"lcov installed on system, continue" \
+	"lcov not installed, abort"
+
+# 4. Create a "tracefile" through lcov, which is necessary to create html files later on.
+echo -n "Creating tracefile for html generation... " 
+verify-run "lcov --no-external --capture --directory . --output-file $COVERAGE_FILE"
+
+for TARGET in $REMOVE_TARGETS; do
+	echo -n "Getting rid of $TARGET files from tracefile... "
+	verify-run "lcov --remove $COVERAGE_FILE $TARGET --output-file $COVERAGE_FILE"
+done
+
+# 5. Create HTML files. 
+echo -n "Creating HTML files... "
+verify-run "genhtml -q -o $COVERAGE_HTML_DIR $COVERAGE_FILE"