libimagequant added as a git submodule (sorry!)

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "lib"]
+	path = lib
+	url = https://github.com/ImageOptim/libimagequant.git

INSTALL

@@ -1,4 +1,8 @@
-To build pngquant from source on Mac OS X and most Linux distributions,
+To get the code:
+
+      $ git clone --recursive https://github.com/pornel/pngquant.git
+
+To build pngquant from source on macOS and most Linux distributions,
 simply run:
 
       $ make

Makefile

@@ -24,12 +24,12 @@ TESTBIN = test/test
 
 all: $(BIN)
 
-staticlib:
+staticlib: lib/libimagequant.h
 	$(MAKE) -C lib static
 
 $(STATICLIB): config.mk staticlib
 
-sharedlib:
+sharedlib: lib/libimagequant.h
 	$(MAKE) -C lib shared
 
 $(SHAREDLIB): config.mk sharedlib
@@ -86,10 +86,13 @@ distclean: clean
 	$(MAKE) -C lib distclean
 	rm -f config.mk pngquant-*-src.tar.gz
 
-config.mk:
+config.mk: lib/libimagequant.h
 ifeq ($(filter %clean %distclean, $(MAKECMDGOALS)), )
 	./configure
 endif
 
+lib/libimagequant.h:
+	git submodule init && git submodule update
+
 .PHONY: all clean dist distclean dll install uninstall test staticlib
 .DELETE_ON_ERROR: