Add Mux library for manipulating WebP container.

This change adds the WebP Mux library for manipulating the WebP Mux
Container. The library document and command line tool exhibiting the
usage of this libary will follow in subsequent Git change.

Change-Id: I4cba7dd12307483185ad5a68df33af6c36c154c8

makefile.unix

@@ -2,7 +2,7 @@
 # system, for simple local building of the libraries and tools.
 # It will not install the libraries system-wide, but just create the 'cwebp'
 # and 'dwebp' tools in the examples/ directory, along with the static
-# library 'src/libwebp.a'.
+# libraries 'src/libwebp.a' and 'src/mux/libwebpmux.a'.
 #
 # To build the library and examples, use:
 #    make -f makefile.unix
@@ -77,9 +77,9 @@ HDRS = src/webp/encode.h src/enc/vp8enci.h src/enc/cost.h \
        src/dsp/yuv.h src/dsp/dsp.h \
        src/utils/bit_writer.h src/utils/bit_reader.h src/utils/thread.h
 
-OUTPUT = examples/cwebp examples/dwebp src/libwebp.a
+OUTPUT = examples/cwebp examples/dwebp src/libwebp.a src/mux/libwebpmux.a
 
-all:ex
+all:ex src/mux/libwebpmux.a
 
 %.o: %.c $(HDRS)
 	$(CC) $(CFLAGS) -c $< -o $@
@@ -87,6 +87,11 @@ all:ex
 src/libwebp.a:  $(OBJS)
 	$(AR) $(ARFLAGS) $@ $^
 
+MUX_OBJS = src/mux/mux.o
+
+src/mux/libwebpmux.a:  $(MUX_OBJS)
+	$(AR) $(ARFLAGS) $@ $^
+
 ex: examples/cwebp examples/dwebp
 
 examples/cwebp: examples/cwebp.o src/libwebp.a
@@ -116,6 +121,7 @@ clean:
               src/dec/*.o src/dec/*~ \
               src/dsp/*.o src/dsp/*~ \
               src/utils/*.o src/utils/*~ \
+              src/mux/*.o src/mux/*~ \
               examples/*.o examples/*~
 
 superclean: clean