Fix #94: compatibility with gimp v2 again

This adds a second version of the gimpscript file containing the script
for gimp v2 (i.e. the version as it was before the previous commit). The
makefile now checks the gimp version and selects which of the two script
files to use based on that.

It would be nicer if the script itself checked the gimp version and
adapted accordingly, but it seems gimp v3 uses a newer scheme version
and newer syntactical elements (i.e. "#:foo" symbols) that the version
in gimp v2 does not understand, making this hard or impossible (at least
for an inexperienced scheme programmer).

This commit is intentionally separate from the previous commit (which
adapts the script for v3 compatibility), so the diff for the previous
commit is easier to read.

This is the last part to fix #94.

Author: matthijskooijman

scripts/gimpscript-v2

@@ -0,0 +1,97 @@
+;----------script-fu-set-all-layers-invisible----------
+;procedure by Hevan53
+;------------------------------------------------------
+
+(define (script-fu-set-all-layers-invisible inImage inDrawable)
+        (let*  (
+                (layers (gimp-image-get-layers inImage))
+                (num-layers (car layers))
+                (layer-array (cadr layers))
+                (theLayer)
+               )
+
+        (gimp-image-undo-group-start inImage)
+
+        (while (> num-layers 0)
+                (set! num-layers (- num-layers 1))
+                (set! theLayer (aref layer-array num-layers))
+                (if (= (car (gimp-drawable-get-visible theLayer) ) TRUE)
+					(gimp-drawable-set-visible theLayer FALSE)
+                )
+        )
+
+        (gimp-image-undo-group-end inImage)
+        (gimp-displays-flush)
+
+        )
+)
+
+;--------------------save-layers-----------------------
+;procedure by planetmaker
+;
+; // List of source and target images followed by a list of layer names
+; // in the source image which will make up the target image.
+;
+; // Example:
+; // (save-layers "source-file-name" "target-file-name" '(layername1 layername2 layername3 ...))
+;------------------------------------------------------
+(define
+	(
+		save-layers
+
+		inImageName
+		outImageName
+		inLayerNames
+	)
+	(let*
+		(
+			(image (car (gimp-file-load RUN-NONINTERACTIVE inImageName inImageName)))
+			(visibleStuff (car (gimp-image-get-active-layer image)))
+        	(layers (gimp-image-get-layers image))
+        	(num-layers (car layers))
+        	(layer-array (cadr layers))
+        	(thisLayer -1)
+			(thisNumLayers 0)
+			(theseLayers layers)
+			(thisLayerName 0)
+
+			(layerNames inLayerNames)
+		)
+
+		; First make everything invisble
+		(script-fu-set-all-layers-invisible image image)
+
+		; Now make those layers visible which were asked to become visible
+
+		; iterate through all layers of the image
+		(while (> num-layers 0)
+			(set! num-layers (- num-layers 1))
+            (set! thisLayer (aref layer-array num-layers))
+			(set! thisLayerName (car (gimp-drawable-get-name thisLayer)))
+			; (gimp-message (string-append "Image Layer-Name: " thisLayerName))
+
+			; iterate through all layer Names we shall use
+			(set! layerNames inLayerNames)
+			(while (not (null? layerNames))
+				; if layerName matches this user supplied layername: make it visible
+				(if (string=? (car layerNames) thisLayerName)
+					(gimp-drawable-set-visible thisLayer TRUE)
+				)
+				(set! layerNames (cdr layerNames))
+			)
+		)
+
+		; Merge all visible layers into one layer which we then save to the given filename
+		(set! visibleStuff (car (gimp-image-merge-visible-layers image CLIP-TO-IMAGE)))
+		(file-png-save RUN-NONINTERACTIVE image visibleStuff outImageName outImageName 0 9 0 0 0 0 0)
+		(gimp-image-delete image)
+	)
+)
+
+
+; // ===================================================================
+; // List of source and target images followed by a list of layer names
+; // in the source image which will make up the target image.
+; // Example:
+; // (save-layers "source-file-name" "target-file-name" '(layername1 layername2 layername3 ...))
+; // ===================================================================