Added script to find bad doxygen references

Usage:
python check_tools/find_bad_doxy_references.py docs/reference

Author: geky

check_tools/find_bad_doxy_references.py

@@ -0,0 +1,52 @@
+#!/usr/bin/env python
+
+import os
+import sys
+import re
+import requests
+
+PATTERN = (
+    "\[!\[View code\]\(https://www\.mbed\.com/embed/\?type=library\)\]"
+    "\((.*)\)"
+)
+
+def main(path):
+    bad = False
+
+    for dir, dirs, files in os.walk(path):
+        for file in files:
+            if not file.endswith('.md'):
+                continue
+
+            path = os.path.join(dir, file)
+            with open(path) as file:
+                for i, line in enumerate(file):
+                    for match in re.findall(PATTERN, line):
+                        if match.startswith('https:'):
+                            sys.stderr.write("\n%s:%s: Bad URL (https):\n" % (path, i))
+                            sys.stderr.write(match + '\n')
+                            bad = True
+
+                        try:
+                            code = requests.get(match).status_code
+                        except requests.exceptions.RequestException:
+                            code = -1
+
+                        if code != 200:
+                            sys.stderr.write("\n%s:%s: Bad URL (%d):\n" % (path, i, code))
+                            sys.stderr.write(match + '\n')
+                            bad = True
+
+                        sys.stdout.write('.')
+                        sys.stdout.flush()
+
+        for dir in dirs:
+            if dir.startswith('.'):
+                dirs.remove(dir)
+
+    sys.stdout.write('\nDone!\n')
+    return 0 if not bad else 1
+
+
+if __name__ == "__main__":
+    sys.exit(main(*sys.argv[1:]))