[devel]  Implemented remaining "_fixed" functions and corrected warnings

that were recently introduced, mostly resulting from
safe but uncast assignments to shorter integers.  Also added a zlib
VStudio release library project because the latest zlib Official Windows
build does not include such a thing.
diff --git a/scripts/symbols.def b/scripts/symbols.def
index 129efd6..8eee808 100644
--- a/scripts/symbols.def
+++ b/scripts/symbols.def
@@ -214,11 +214,11 @@
  png_save_int_32 @206
  png_save_uint_16 @207
  png_set_gamma_fixed @208
-; png_set_filter_heuristics_fixed @209
-; png_get_pixel_aspect_ratio_fixed @210
+ png_set_filter_heuristics_fixed @209
+ png_get_pixel_aspect_ratio_fixed @210
  png_get_x_offset_inches_fixed @211
  png_get_y_offset_inches_fixed @212
-; png_set_sCAL_fixed @213
+ png_set_sCAL_fixed @213
  png_get_sCAL_fixed @214
  png_get_num_passes @215
  png_get_num_rows @216