Add trim to ZString.

ZString.cpp

@@ -397,6 +397,11 @@ namespace coreutils {
       return ZString(temp, tempend - temp);
    }
 
+   ZString ZString::trim() {
+      skipWhitespace();
+      return unparsed();
+   }
+
    int ZString::find(ZString comparator) {
       int count = 0;
       char *temp = cursor;