Added method used to check if a Regexp is valid.

git-svn-id: http://voip.null.ro/svn/yate@6094 acf43c95-373e-0410-b603-e72c3f656dc1

yateclass.h

@@ -2915,6 +2915,13 @@ public:
     inline Regexp& operator=(const char* value)
 	{ String::operator=(value); return *this; }
 
+    /**
+     * Check if the regular expression is valid
+     * @return True if valid, false if not
+     */
+    inline bool valid() const
+	{ return m_regexp != 0; }
+
     /**
      * Makes sure the regular expression is compiled
      * @return True if successfully compiled, false on error