tools: Download gas-pp from libav.org instead of from github

The github repo is only a mirror while the libav.org one is the
upstream.
Signed-off-by: Martin Storsjö <martin@martin.st>

extras/tools/packages.mak

@@ -33,7 +33,7 @@ OPENSSL_VERSION=1.0.0e
 OPENSSL_URL=http://www.openssl.org/source/openssl-$(OPENSSL_VERSION).tar.gz
 
 GAS_VERSION=c76b628
-GAS_URL=https://github.com/libav/gas-preprocessor/tarball/$(GAS_VERSION)
+GAS_URL=http://git.libav.org/?p=gas-preprocessor.git;a=snapshot;h=$(GAS_VERSION);sf=tgz
 
 RAGEL_VERSION=6.8
 RAGEL_URL=http://www.complang.org/ragel/ragel-$(RAGEL_VERSION).tar.gz

extras/tools/tools.mak

@@ -216,10 +216,10 @@ CLEAN_PKG += openssl
 DISTCLEAN_PKG += openssl-$(OPENSSL_VERSION).tar.gz
 
 # gas-preprocessor
-libav-gas-preprocessor-$(GAS_VERSION).tar.gz:
+gas-preprocessor-$(GAS_VERSION).tar.gz:
 	$(call download,$(GAS_URL))
 
-gas: libav-gas-preprocessor-$(GAS_VERSION).tar.gz
+gas: gas-preprocessor-$(GAS_VERSION).tar.gz
 	$(UNPACK)
 	$(MOVE)