sipcalc: use autorelease feature

Package version is automatically increased as described here:
openwrt#14537

Signed-off-by: Nick Hainke <vincent@systemli.org>

utils/sipcalc/Makefile

@@ -6,7 +6,7 @@ include $(TOPDIR)/rules.mk
 
 PKG_NAME:=sipcalc
 PKG_SOURCE_DATE:=2014-10-24
-PKG_RELEASE:=1
+PKG_RELEASE:=$(AUTORELEASE)
 
 PKG_SOURCE_PROTO:=git
 PKG_SOURCE_URL:=https://github.com/sii/sipcalc