Fix libmpcdec update

src/libmpcdec.mk

@@ -11,10 +11,8 @@ $(PKG)_URL      := https://files.musepack.net/source/$(PKG)-$($(PKG)_VERSION).ta
 $(PKG)_DEPS     := cc
 
 define $(PKG)_UPDATE
-    $(WGET) -q -O- 'https://files.musepack.net/source/$(PKG)-$($(PKG)_VERSION)' | \
-    $(SED) -n 's,.*$(PKG)-\([0-9][^>]*\)\.tar.*,\1,p' | \
-    grep -v 'alpha' | \
-    grep -v 'beta' | \
+    $(WGET) -q -O- 'http://svn.musepack.net/libmpcdec/tags/' | \
+    $(SED) -n "s,.*>release-\([0-9]\+\.[0-9]\+\.[0-9]\+\).*,\1,p" | \
     $(SORT) -Vr | \
     head -1
 endef