contrib: add bpg

Currently libbpg is only available as a static library.

contrib/src/bpg/SHA512SUMS

+8b97327d7bd9af41e88daa226e8791d797e6ff1ac01fe3ab25e2a64e193d80b51364ff76371dc9b99fa19da2d5d3e9301b5a2fe396b4014601175f5e8d0274ba  libbpg-0.9.4.tar.gz

contrib/src/bpg/pic.patch

+--- libbpg-0.9.4/Makefile.old	2015-01-07 15:41:29.030598098 -0500
++++ libbpg-0.9.4/Makefile	2015-01-07 15:51:18.146608993 -0500
+@@ -36,7 +36,7 @@
+ 
+ PWD:=$(shell pwd)
+ 
+-CFLAGS:=-Os -Wall -MMD -fno-asynchronous-unwind-tables -fdata-sections -ffunction-sections -fno-math-errno -fno-signed-zeros -fno-tree-vectorize -fomit-frame-pointer
++CFLAGS+=-Os -Wall -MMD -fno-asynchronous-unwind-tables -fdata-sections -ffunction-sections -fno-math-errno -fno-signed-zeros -fno-tree-vectorize -fomit-frame-pointer
+ CFLAGS+=-D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -D_REENTRANT
+ CFLAGS+=-I.
+ CFLAGS+=-DCONFIG_BPG_VERSION=\"$(shell cat VERSION)\"

contrib/src/bpg/rules.mak

+# BPG
+BPG_VERSION := 0.9.4
+BPG_URL := http://bellard.org/bpg/libbpg-$(BPG_VERSION).tar.gz
+
+# default disabled
+# PKGS += bpg
+
+$(TARBALLS)/libbpg-$(BPG_VERSION).tar.gz:
+	$(call download,$(BPG_URL))
+
+.sum-bpg: libbpg-$(BPG_VERSION).tar.gz
+
+bpg: libbpg-$(BPG_VERSION).tar.gz .sum-bpg
+	$(UNPACK)
+	$(APPLY) $(SRC)/bpg/pic.patch
+	$(MOVE)
+
+.bpg: bpg
+	cd $< && $(HOSTVARS_PIC) $(MAKE) libbpg.a
+	mkdir -p $(PREFIX)/include/ && cp $</libbpg.h $(PREFIX)/include/
+	mkdir -p $(PREFIX)/lib/ && cp $</libbpg.a $(PREFIX)/lib/
+	touch $@