update changelog

ChangeLog

@@ -19,6 +19,7 @@
 - add VipsStream: a universal IO class for loaders and savers
 - jpeg, png, tiff (though not tiffsave), rad, svg, ppm and webp use the 
   new IO class
+- rewritten ppm load/save is faster and uses less memory
 - add @no_strip option to dzsave [kalozka1]
 - add iiif layout to dzsave
 - fix use of resolution-unit metadata on tiff save [kayarre]

libvips/foreign/ppmload.c

@@ -33,6 +33,8 @@
  * 	- fix a loop with malformed ppm
  * 13/11/19
  * 	- redone with streams
+ * 	- sequential load, plus mmap for filename streams
+ * 	- faster plus lower memory use
  */
 
 /*
@@ -62,11 +64,6 @@
 
  */
 
-/* TODO
- *
- * - load filename streams with mmap 
- */
-
 /*
 #define DEBUG
  */

libvips/foreign/ppmsave.c

@@ -2,6 +2,9 @@
  *
  * 2/12/11
  * 	- wrap a class around the ppm writer
+ * 13/11/19
+ * 	- redone with streams
+ * 	- faster plus lower memory use
  */
 
 /*