support comments in dsn files

pcbnew/dsn.cpp

@@ -601,13 +601,23 @@ L_read:
                 goto exit;
             }
             
-            cur = next;
+            cur = start;
-        }
             
             // skip leading whitespace
             while( cur<limit && isspace(*cur) )
                 ++cur;
 
+            // if the first non-blank character is #, this line is a comment.
+            if( cur<limit && *cur=='#' )
+                goto L_read;
+        }
+        else
+        {
+            // skip leading whitespace
+            while( cur<limit && isspace(*cur) )
+                ++cur;
+        }
+
         if( cur >= limit )
             goto L_read;