Define in terms of privincludedir. (camellibexecdir): Define in terms of

Define in terms of privincludedir. (camellibexecdir): Define in terms of

	* Makefile.am (libcamelincludedir): Define in terms of
	privincludedir.
	(camellibexecdir): Define in terms of privlibexecdir
	(libcamel_la_LDFLAGS): Remove -rpath. (automake will add that)

	* providers/imap/Makefile.am (libcamelimapincludedir): Define in
	terms of privincludedir.
	(INCLUDES): Remove -I$(includedir)
	* providers/local/Makefile.am: Likewise
	* providers/nntp/Makefile.am: Likewise
	* providers/pop3/Makefile.am: Likewise
	* providers/sendmail/Makefile.am: Likewise
	* providers/smtp/Makefile.am: Likewise