Add lodepng

.gitmodules

@@ -1,3 +1,6 @@
 [submodule "external/tinystl"]
 	path = external/tinystl
 	url = git://github.com/mendsley/tinystl.git
+[submodule "external/lodepng"]
+	path = external/lodepng
+	url = https://github.com/lvandeve/lodepng.git

external/lodepng

@@ -0,0 +1 @@
+Subproject commit 9f3acec682697642ebccdf8659c8b53bf05001f1

external/rules.mk

@@ -3,3 +3,6 @@ external_LOCAL_PATH := $(call whereami)
 include $(wildcard $(external_LOCAL_PATH)/*/rules.mk)
 
 INCLUDE_EXT += $(external_LOCAL_PATH)/tinystl/include
+INCLUDE_EXT += $(external_LOCAL_PATH)/lodepng
+
+SRCS_CPP += $(external_LOCAL_PATH)/lodepng/lodepng.cpp