samba4: security bump to version 4.5.15

Fixes the following security issues:

- CVE-2017-14746:
  All versions of Samba from 4.0.0 onwards are vulnerable to a use after
  free vulnerability, where a malicious SMB1 request can be used to
  control the contents of heap memory via a deallocated heap pointer. It
  is possible this may be used to compromise the SMB server.

- CVE-2017-15275:
  All versions of Samba from 3.6.0 onwards are vulnerable to a heap
  memory information leak, where server allocated heap memory may be
  returned to the client without being cleared.

  There is no known vulnerability associated with this error, but
  uncleared heap memory may contain previously used data that may help
  an attacker compromise the server via other methods. Uncleared heap
  memory may potentially contain password hashes or other high-value
  data.

For more details, see the release notes:
https://www.samba.org/samba/history/samba-4.5.15.html

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/samba4/samba4.hash

@@ -1,2 +1,2 @@
 # Locally calculated
-sha256  15dc04fd2b19081daf1118318f43f88ef7260b3fc6e4f86ee7c7913bb7c92ed9 samba-4.5.14.tar.gz
+sha256  811bf727892a1e1e3d170eb72eb39c43d06ed8ff557e5e036a41aabc19008e94 samba-4.5.15.tar.gz

package/samba4/samba4.mk

@@ -4,7 +4,7 @@
 #
 ################################################################################
 
-SAMBA4_VERSION = 4.5.14
+SAMBA4_VERSION = 4.5.15
 SAMBA4_SITE = https://download.samba.org/pub/samba/stable
 SAMBA4_SOURCE = samba-$(SAMBA4_VERSION).tar.gz
 SAMBA4_INSTALL_STAGING = YES