gnu: Add woff2.

* gnu/packages/fontutils.scm (woff2): New variable.
* gnu/packages/patches/woff2-libbrotli.patch: New patch.
* gnu-system.am (dist_patch_DATA): Add it.

gnu/packages/patches/woff2-libbrotli.patch

@@ -0,0 +1,84 @@
+From: Eric Bavier <bavier@member.fsf.org>
+Date: Sat, 2 Apr 2016 01:31:03 -0500
+Subject: [PATCH] Build against external libbrotli.
+
+---
+ Makefile         | 20 ++++----------------
+ src/woff2_dec.cc |  2 +-
+ src/woff2_enc.cc |  2 +-
+ 3 files changed, 6 insertions(+), 18 deletions(-)
+
+diff --git a/Makefile b/Makefile
+index 92b8d54..618a751 100644
+--- a/Makefile
++++ b/Makefile
+@@ -1,6 +1,6 @@
+ OS := $(shell uname)
+ 
+-CPPFLAGS = -I./brotli/dec/ -I./brotli/enc/ -I./src
++CPPFLAGS := -I./src $(shell pkg-config --cflags libbrotlienc libbrotlidec)
+ 
+ CC ?= gcc
+ CXX ?= g++
+@@ -22,29 +22,17 @@ OUROBJ = font.o glyph.o normalize.o table_tags.o transform.o \
+          woff2_dec.o woff2_enc.o woff2_common.o woff2_out.o \
+          variable_length.o
+ 
+-BROTLI = brotli
+-ENCOBJ = $(BROTLI)/enc/*.o
+-DECOBJ = $(BROTLI)/dec/*.o
++BROTLI_LIBS := $(shell pkg-config --libs libbrotlienc libbrotlidec)
+ 
+ OBJS = $(patsubst %, $(SRCDIR)/%, $(OUROBJ))
+ EXECUTABLES=woff2_compress woff2_decompress
+ 
+ EXE_OBJS=$(patsubst %, $(SRCDIR)/%.o, $(EXECUTABLES))
+ 
+-ifeq (,$(wildcard $(BROTLI)/*))
+-  $(error Brotli dependency not found : you must initialize the Git submodule)
+-endif
+-
+ all : $(OBJS) $(EXECUTABLES)
+ 
+-$(EXECUTABLES) : $(EXE_OBJS) deps
+-	$(CXX) $(LFLAGS) $(OBJS) $(ENCOBJ) $(DECOBJ) $(SRCDIR)/$@.o -o $@
+-
+-deps :
+-	$(MAKE) -C $(BROTLI)/dec
+-	$(MAKE) -C $(BROTLI)/enc
++$(EXECUTABLES) : $(EXE_OBJS)
++	$(CXX) $(LDFLAGS) $(OBJS) $(SRCDIR)/$@.o -o $@ $(BROTLI_LIBS) $(LIBS)
+ 
+ clean :
+ 	rm -f $(OBJS) $(EXE_OBJS) $(EXECUTABLES)
+-	$(MAKE) -C $(BROTLI)/dec clean
+-	$(MAKE) -C $(BROTLI)/enc clean
+diff --git a/src/woff2_dec.cc b/src/woff2_dec.cc
+index 837eede..98c01ce 100644
+--- a/src/woff2_dec.cc
++++ b/src/woff2_dec.cc
+@@ -27,7 +27,7 @@
+ #include <memory>
+ #include <utility>
+ 
+-#include "./decode.h"
++#include "brotli/dec/decode.h"
+ #include "./buffer.h"
+ #include "./port.h"
+ #include "./round.h"
+diff --git a/src/woff2_enc.cc b/src/woff2_enc.cc
+index 920c614..00d74da 100644
+--- a/src/woff2_enc.cc
++++ b/src/woff2_enc.cc
+@@ -23,7 +23,7 @@
+ #include <string>
+ #include <vector>
+ 
+-#include "./encode.h"
++#include "brotli/enc/encode.h"
+ #include "./buffer.h"
+ #include "./font.h"
+ #include "./normalize.h"
+-- 
+2.7.3
+