cpp2ffi: explicit str_subst

generator/cpp2ffi.lua

@@ -2198,9 +2198,13 @@ function M.Parser()
 		local txt = table.concat(cdefs2,"\n")
 		--string substitution
 		if self.str_subst then
+			print("========== str_subst")
+			local nn
 			for k,v in pairs(self.str_subst) do
-				txt = txt:gsub(k,v)
+				txt,nn = txt:gsub(k,v)
+				print(k,"done times:",nn)
 			end
+			print("========== str_subst end")
 		end
 		--clean = default in constructor (implot3d)
 		txt = txt:gsub("=%s*default","")