Improve C++ and Python APIs.

* include/mailutils/cpp/header.h (Header.has_key): New method.
* libmu_cpp/header.cc: Likewise.
* include/mailutils/cpp/mailbox.h (MailboxDefault): Make name optional.
* libmu_cpp/mailbox.cc: Likewise.
* python/mailutils/header.py (__contains__, has_key): New method.

@@ -38,6 +38,7 @@ class Header
   Header ();
   Header (const mu_header_t);
 
+  bool has_key (const std::string& name);
   std::string get_value (const std::string& name);
   std::string get_value (const std::string& name, const std::string& def);
   size_t size ();

@@ -76,6 +76,7 @@ class Mailbox : public MailboxBase
 class MailboxDefault : public MailboxBase
 {
  public:
+  MailboxDefault ();
   MailboxDefault (const std::string&);
   MailboxDefault (const mu_mailbox_t);
   ~MailboxDefault ();

@@ -39,6 +39,20 @@ Header :: Header (const mu_header_t hdr)
   this->hdr = hdr;
 }
 
+bool
+Header :: has_key (const std::string& name)
+{
+  const char* buf = NULL;
+
+  int status = mu_header_sget_value (hdr, name.c_str (), &buf);
+  if (status == MU_ERR_NOENT)
+    return false;
+  else if (status)
+    throw Exception ("Header::has_key", status);
+
+  return true;
+}
+
 std::string
 Header :: get_value (const std::string& name)
 {

@@ -226,6 +226,13 @@ Mailbox :: ~Mailbox ()
 // MailboxDefault
 //
 
+MailboxDefault :: MailboxDefault ()
+{
+  int status = mu_mailbox_create_default (&mbox, NULL);
+  if (status)
+    throw Exception ("MailboxDefault::MailboxDefault", status);
+}
+
 MailboxDefault :: MailboxDefault (const std::string& name)
 {
   int status = mu_mailbox_create_default (&mbox, name.c_str ());

@@ -38,6 +38,14 @@ class Header:
     def __setitem__ (self, name, value):
         self.set_value (name, value)
 
+    def __contains__ (self, name):
+        status, value = header.get_value (self.hdr, name)
+        if status == MU_ERR_NOENT:
+            return False
+        elif status:
+            raise HeaderError (status)
+        return True
+
     def __getattr__ (self, name):
         if name == 'size':
             return self.get_size ()
@@ -62,6 +70,9 @@ class Header:
             self.__count += 1
             return self.__getitem__ (self.__count)
 
+    def has_key (self, name):
+        return self.__contains__ (name)
+
     def get_size (self):
         status, size = header.size (self.hdr)
         if status: