New function that now holds the main logic of the old camel_pstring_strdup

New function that now holds the main logic of the old camel_pstring_strdup

2006-07-06  Jeffrey Stedfast  <fejj@novell.com>

	* camel-string-utils.c (camel_pstring_add): New function that now
	holds the main logic of the old camel_pstring_strdup function. If
	'own' is TRUE, re-use the memory if the string doesn't already
	exist and free it otherwise. If FALSE, strdup the value if it
	doesn't already exist.
	(camel_pstring_strdup): Calls camel_pstring_add() with 'own' as
	FALSE.

	* camel-folder-summary.c (message_info_new_from_header): Use
	camel_pstring_add instead of camel_pstring_strdup here to prevent
	unnecessary strdup/freeing.
	(message_info_load): Same.