[libpng16] Update "last changed" dates in recently-patched files.

arm/arm_init.c

@@ -90,7 +90,7 @@ safe_read(png_structp png_ptr, int fd, void *buffer_in, size_t nbytes)
          if (errno != EINTR)
          {
             png_warning(png_ptr, "/proc read failed");
-            return 0; /* I.e. a permanent failure */
+            return 0; /* I.e., a permanent failure */
          }
       }
 

arm/filter_neon_intrinsics.c

@@ -21,7 +21,7 @@
 
 /* libpng row pointers are not necessarily aligned to any particular boundary,
  * however this code will only work with appropriate alignment.  arm/arm_init.c
- * checks for this (and will not compile unless it is done), this code uses
+ * checks for this (and will not compile unless it is done). This code uses
  * variants of png_aligncast to avoid compiler warnings.
  */
 #define png_ptr(type,pointer) png_aligncast(type *,pointer)