protobuf: Update version to 2.6.1

- Unbroke MIPS support which got entirely lost since the upgrade from 2.4.1:
  now all ISAs should work (MIPS1 would need kernel emulation though, untested)
- Fixed host installation which was broken on all targets
- Updated source origin to github and related variables
- Kept mipseb patch exception and MIPS16:=0 exclusion (needed for BB and CC compilation)

Only tested on a ZyXEL NBG6716 router which is MIPS32 (MIPS74Kc), ar71xx target.

Signed-off-by: Guillaume Déflache <guillaume.deflache@ibwag.com>

libs/protobuf/Makefile

@@ -8,18 +8,18 @@
 include $(TOPDIR)/rules.mk
 
 PKG_NAME:=protobuf
-PKG_VERSION:=2.5.0
+PKG_VERSION:=2.6.1
 PKG_RELEASE:=1
 
 PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.bz2
-PKG_SOURCE_URL:=http://protobuf.googlecode.com/files
-PKG_MD5SUM:=a72001a9067a4c2c4e0e836d0f92ece4
+PKG_SOURCE_URL:=https://github.com/google/protobuf/releases/download/v$(PKG_VERSION)
+PKG_MD5SUM:=11aaac2d704eef8efd1867a807865d85
 
 PKG_LICENSE:=BSD-3-Clause
 PKG_LICENSE_FILES:=LICENSE
 
 PKG_BUILD_DEPENDS:=protobuf/host
-PKG_USE_MIPS16:=0
+PKG_USE_MIPS16:=0# MIPS16 prevents protobuf's usage of the 'sync' asm-opcode
 
 PKG_INSTALL:=1
 
@@ -41,15 +41,7 @@ define Package/protobuf/description
  of its internal RPC protocols and file formats.
 endef
 
-define Host/Compile
-	$(MAKE) -C $(HOST_BUILD_DIR)
-endef
-
-define Host/Install
-	$(MAKE) -C $(HOST_BUILD_DIR) install
-endef
-
-CONFIGURE_ARGS += --with-protoc=$(HOST_BUILD_DIR)/src/protoc
+CONFIGURE_ARGS += --with-protoc=$(STAGING_DIR_HOST)/bin/protoc
 
 define Build/InstallDev
 	$(INSTALL_DIR) \