Sounds: Update Makefile for Extra sounds 1.5.1 release

Incrementing version for the Extra sounds release. 1.5.1 Extra sounds
removes two prompts that were moved into the Core packages in the 1.6 Core
sounds release.

ASTERISK-27142 #close

Change-Id: I82f017812b0ea9599e19dd4635afd55611f13ee7

sounds/Makefile

@@ -20,7 +20,7 @@ SOUNDS_DIR:=$(DESTDIR)$(ASTDATADIR)/sounds
 SOUNDS_CACHE_DIR?=
 MOH_DIR:=$(DESTDIR)$(ASTDATADIR)/moh
 CORE_SOUNDS_VERSION:=1.6
-EXTRA_SOUNDS_VERSION:=1.5
+EXTRA_SOUNDS_VERSION:=1.5.1
 MOH_VERSION:=2.03
 SOUNDS_URL:=http://downloads.asterisk.org/pub/telephony/sounds/releases
 MCS:=$(subst -EN-,-en-,$(MENUSELECT_CORE_SOUNDS))