Made CONCAT-STRING use the buffer join technique rather than the + operator which is notoriously slow for string concatenation in some browsers.
Made CONCAT-STRING use the buffer join technique rather than the +
operator which is notoriously slow for string concatenation in some
browsers.

fredericksilva/Parenscript,manuel/parenscript,vsedach/Parenscript,JDReutt/parenscript,VincentToups/parenscript,3b/parenscript