implement startsWith and endsWith.

Foundation/include/Poco/String.h

@@ -623,6 +623,22 @@ S cat(const S& delim, const It& begin, const It& end)
 }
 
 
+template <class S>
+bool startsWith(const S& str, const S& prefix)
+	/// Tests whether the string starts with the given prefix.
+{
+	return equal(prefix.begin(), prefix.end(), str.begin());
+}
+
+
+template <class S>
+bool endsWith(const S& str, const S& suffix)
+	/// Tests whether the string ends with the given suffix.
+{
+	return equal(suffix.rbegin(), suffix.rend(), str.rbegin());
+}
+
+
 //
 // case-insensitive string equality
 //