Add port of libspng-0.4.3

Fixes #148.

lib/import/import-libspng.mk

@@ -0,0 +1,2 @@
+LIBSPNG_PORT_DIR := $(call select_from_ports,libspng)
+INC_DIR += $(LIBSPNG_PORT_DIR)/include/spng

lib/mk/libspng.mk

@@ -0,0 +1,13 @@
+include $(REP_DIR)/lib/import/import-libspng.mk
+
+LIBSPNG_SRC_DIR := $(LIBSPNG_PORT_DIR)/src/lib/libspng/src
+
+SRC_C := common.c decode.c
+
+LIBS += libc zlib
+
+vpath %.c $(LIBSPNG_SRC_DIR)
+
+SHARED_LIB := yes
+
+CC_CXX_WARN_STRICT :=

lib/symbols/libspng

@@ -0,0 +1,46 @@
+spng_ctx_free T
+spng_ctx_new T
+spng_ctx_new2 T
+spng_decode_image T
+spng_decoded_image_size T
+spng_get_bkgd T
+spng_get_chrm T
+spng_get_chrm_int T
+spng_get_exif T
+spng_get_gama T
+spng_get_hist T
+spng_get_iccp T
+spng_get_ihdr T
+spng_get_image_limits T
+spng_get_offs T
+spng_get_phys T
+spng_get_plte T
+spng_get_sbit T
+spng_get_splt T
+spng_get_srgb T
+spng_get_text T
+spng_get_time T
+spng_get_trns T
+spng_set_bkgd T
+spng_set_chrm T
+spng_set_chrm_int T
+spng_set_crc_action T
+spng_set_exif T
+spng_set_gama T
+spng_set_hist T
+spng_set_iccp T
+spng_set_ihdr T
+spng_set_image_limits T
+spng_set_offs T
+spng_set_phys T
+spng_set_plte T
+spng_set_png_buffer T
+spng_set_png_stream T
+spng_set_sbit T
+spng_set_splt T
+spng_set_srgb T
+spng_set_text T
+spng_set_time T
+spng_set_trns T
+spng_strerror T
+spng_version_string T