flac: update to v1.3.1 (CVE-2014-8962, CVE-2014-9028)

This updates flac to the new upstream release v1.3.1 to fix two known CVEs.

Additionally the commit changes the following:
 * Drop custom Build/Configure recipe in favor to CONFIGURE_ARGS
 * Refreshes patches and removes changes to *.in files since they're
   regenerated by autoreconf anyway
 * Remove now obsolete 020-libFLAC-remove-altivec-options.patch
 * Add an md5sum for the source archive
 * Passes --enable-static to configure to force producing a libflac.a

Signed-off-by: Jo-Philipp Wich <jow@openwrt.org>

libs/flac/patches/002-no-utility.patch

@@ -1,24 +1,13 @@
 --- a/src/Makefile.am
 +++ b/src/Makefile.am
-@@ -26,9 +26,6 @@ endif
+@@ -27,10 +27,7 @@ endif
  SUBDIRS = \
- 	libFLAC \
  	share \
+ 	libFLAC \
 -	flac \
 -	metaflac \
--	monkeys_audio_utilities \
- 	$(XMMS_DIRS) \
- 	$(CPPLIBS_DIRS)
- 
---- a/src/Makefile.in
-+++ b/src/Makefile.in
-@@ -226,9 +226,6 @@ target_alias = @target_alias@
- SUBDIRS = \
- 	libFLAC \
- 	share \
--	flac \
--	metaflac \
--	monkeys_audio_utilities \
  	$(XMMS_DIRS) \
+-	utils \
  	$(CPPLIBS_DIRS)
  
+ EXTRA_DIST = \